Showing 1–50 of 87 results for author: Takada, S

Revisiting Stress Analysis in a Three-Dimensional Elastic Hollow Sphere under Uniaxial Compression via the Inverse Laplace Transform Expressions within an Elastodynamic Framework

Authors: Satoshi Takada, Shintaro Hokada

Abstract: The stress analysis of a three-dimensional elastic hollow sphere subjected to uniaxial compression is revisited, employing an elastodynamic framework. Through the application of the Laplace transform, the scalar and vector potentials of displacement are expanded, facilitating a detailed exploration of the system's mechanical behavior. The static solutions for displacement and stress distributions… ▽ More The stress analysis of a three-dimensional elastic hollow sphere subjected to uniaxial compression is revisited, employing an elastodynamic framework. Through the application of the Laplace transform, the scalar and vector potentials of displacement are expanded, facilitating a detailed exploration of the system's mechanical behavior. The static solutions for displacement and stress distributions are derived in the long-time limit, which reveal key insights into the response of the elastic hollow sphere. Notably, on the inner surface, certain quantities exhibit a peak at the point where the angle between the compressive force and the point on the surface becomes perpendicular, indicating localized stress concentration. These findings provide a robust analytical approach for understanding and predicting the behavior of elastic hollow spheres under uniaxial loading, with implications for material science and structural engineering. △ Less

Submitted 31 July, 2026; originally announced July 2026.

Comments: 10 pages, 5 figures

Quantum tunneling Mpemba effect

Authors: Hisao Hayakawa, Satoshi Takada

Abstract: The quantum tunneling Mpemba effect is investigated within a continuous one-dimensional symmetric double-well potential open to external environmental sinks at the boundaries ($x=\pm L$). Using a non-Hermitian spectral decomposition of the effective Hamiltonian, we characterize the open-system relaxation dynamics without relying on abstract state-space quenches. We mathematically prove that the no… ▽ More The quantum tunneling Mpemba effect is investigated within a continuous one-dimensional symmetric double-well potential open to external environmental sinks at the boundaries ($x=\pm L$). Using a non-Hermitian spectral decomposition of the effective Hamiltonian, we characterize the open-system relaxation dynamics without relying on abstract state-space quenches. We mathematically prove that the non-monotonic behavior of the first non-trivial even-parity spectral coefficient, $a_{2}(T_{i})$, with respect to the initial preparation temperature $T_{i}$ is a universal topological property born from quantum statistical mechanics. Crucially, we demonstrate that this intermediate thermal peak is governed by the Sturm-Liouville oscillation theorem and remains completely invariant with respect to the global system size $L$, contrasting sharply with the boundary-driven classical Mpemba effect. This universal peak arises from the geometric and nodal alignment between highly localized unperturbed states and extended non-Hermitian decay channels. Furthermore, we clarify that while this mechanism is robust, the actual observation of anomalous crossings in the total survival probability trace $S(t,T_{i})$ and the trace distance $\mathcal{D}(t,T_i)$ demand a strict separation of timescales, requiring the over-barrier escape rate to vastly exceed the decay rate of the deep-well tunneling doublet ($Γ_{2}\gg Γ_{0}$ and $Γ_2\gg Γ_1$). Our continuous formulation successfully bridges real-space classical boundary-driven dissipation with open quantum dynamics, providing novel insights for engineering non-equilibrium states via tailored boundary loss. △ Less

Submitted 4 July, 2026; originally announced July 2026.

Comments: 25 pages, 6 figures

Mpemba effect in a sheared granular gas with velocity-dependent restitution

Authors: Makoto R. Kikuchi, Yuria Kobayashi, Satoshi Takada

Abstract: We investigate the Mpemba effect in a dilute sheared granular gas with a velocity-dependent restitution coefficient. Using kinetic theory based on Grad's moment method, we analyze the relaxation dynamics following a sudden change in the shear rate. We show that, despite having a higher initial temperature, a system starting from an isotropic state can relax faster than a system prepared in a shear… ▽ More We investigate the Mpemba effect in a dilute sheared granular gas with a velocity-dependent restitution coefficient. Using kinetic theory based on Grad's moment method, we analyze the relaxation dynamics following a sudden change in the shear rate. We show that, despite having a higher initial temperature, a system starting from an isotropic state can relax faster than a system prepared in a sheared steady state, demonstrating a clear Mpemba effect in the temperature evolution. We further demonstrate the emergence of a viscosity Mpemba effect, characterized by crossings in the relaxation curves of the shear viscosity. Remarkably, multiple crossings arise due to an additional intrinsic timescale introduced by the velocity dependence of the restitution coefficient, providing a minimal kinetic mechanism for multiple Mpemba effects in driven granular gases. △ Less

Submitted 18 May, 2026; originally announced May 2026.

Comments: 6 pages, 4 figures

Revisiting the Stress Field Inside an Elastic Sphere Subjected to a Concentrated Load

Authors: Yosuke Mori, Kiwamu Yoshii, Satoshi Takada

Abstract: We present a complete analytical solution for the stress field inside a homogeneous, inside a homogeneous, linearly elastic solid sphere subjected to a concentrated normal load applied on its surface. Starting from the three-dimensional linearized elastodynamic equations, the displacement and stress fields are derived using scalar and vector potential representations combined with spherical harmon… ▽ More We present a complete analytical solution for the stress field inside a homogeneous, inside a homogeneous, linearly elastic solid sphere subjected to a concentrated normal load applied on its surface. Starting from the three-dimensional linearized elastodynamic equations, the displacement and stress fields are derived using scalar and vector potential representations combined with spherical harmonic expansions. All expansion coefficients are determined explicitly by enforcing the traction boundary conditions. The static elastic solution is obtained rigorously as the long-time limit of the dynamical formulation. Closed-form expressions for all components of the stress tensor are provided, enabling direct evaluation of the principal stresses and their differences throughout the interior of the sphere. The analytical solution is further generalized to arbitrary loading positions by means of rotational transformations, allowing systematic treatment of multiple concentrated loads through superposition. △ Less

Submitted 4 May, 2026; originally announced May 2026.

Comments: 24 pages, 8 figures

Mpemba effect in a two-dimensional bistable potential

Authors: Hisao Hayakawa, Satoshi Takada

Abstract: We present an exactly solvable model of the Mpemba effect in an overdamped Langevin system confined in a two-dimensional radially symmetric bistable potential. The potential is constructed as a piecewise quadratic-logarithmic function that is continuous and differentiable at the matching radii, enabling an exact mapping of the corresponding Fokker-Planck operator to a Schroedinger-type eigenvalue… ▽ More We present an exactly solvable model of the Mpemba effect in an overdamped Langevin system confined in a two-dimensional radially symmetric bistable potential. The potential is constructed as a piecewise quadratic-logarithmic function that is continuous and differentiable at the matching radii, enabling an exact mapping of the corresponding Fokker-Planck operator to a Schroedinger-type eigenvalue problem. The relaxation spectrum and eigenmodes are obtained analytically in each region in terms of confluent hypergeometric functions, with eigenvalues determined from matching conditions. Focusing on isotropic equilibrium initial states at inverse temperature $β_{\rm ini}$ quenched to a bath at inverse temperature $β$, we derive explicit expressions for the mode amplitudes governing long-time relaxation. We demonstrate that the coefficient of the slowest mode exhibits non-monotonic dependence on $β_{\rm ini}$ and identify a sufficient crossing condition for the Kullback-Leibler divergence in terms of the two slowest modes, if the global minimum of the potential is located far away from the origin and the second minimum exists near the origin. For corresponding parameters, we demonstrate that the Mpemba effect can be realized. Our results provide a rare example of an analytically tractable two-dimensional model exhibiting anomalous relaxation without any confining walls, extending previous one-dimensional constructions with a hard wall and clarifying the role of radial geometry in nonequilibrium relaxation phenomena. △ Less

Submitted 1 April, 2026; v1 submitted 25 March, 2026; originally announced March 2026.

Comments: 26 pages, 12 figures

Discontinuous change of viscosity in a sheared granular gas with velocity-dependent restitution

Authors: Makoto R. Kikuchi, Yuria Kobayashi, Satoshi Takada

Abstract: We investigate the rheology of a sheared granular gas composed of hard spheres with a velocity-dependent restitution coefficient. Using kinetic theory, we derive the shear viscosity and show that it exhibits an S-shaped dependence on the shear rate when the restitution coefficient switches between two values depending on the collision velocity. As a result, a discontinuous change of viscosity emer… ▽ More We investigate the rheology of a sheared granular gas composed of hard spheres with a velocity-dependent restitution coefficient. Using kinetic theory, we derive the shear viscosity and show that it exhibits an S-shaped dependence on the shear rate when the restitution coefficient switches between two values depending on the collision velocity. As a result, a discontinuous change of viscosity emerges between low- and high-shear regimes, both characterized by Bagnold-type scaling. While the phenomenology resembles the Wyart-Cates scenario for dense suspensions, the present transition arises purely from kinetic effects without frictional contacts or jamming. △ Less

Submitted 19 March, 2026; originally announced March 2026.

Comments: 5 pages, 4 figures

Journal ref: J. Phys. Soc. Jpn. 95, 053801 (2026)

Inverse Reconstruction of Moving Contact Loads on an Elastic Half-Space Using Prescribed Surface Displacement

Authors: Satoshi Takada, Yosuke Mori, Shintaro Hokada

Abstract: This study investigates the elastic response of a two-dimensional semi-infinite medium subjected to a moving surface load with a prescribed displacement profile. As a fundamental step, we derive analytical Green's functions for the displacement and stress fields generated by a point load traveling at a constant velocity along the surface, explicitly incorporating elastodynamic effects through Mach… ▽ More This study investigates the elastic response of a two-dimensional semi-infinite medium subjected to a moving surface load with a prescribed displacement profile. As a fundamental step, we derive analytical Green's functions for the displacement and stress fields generated by a point load traveling at a constant velocity along the surface, explicitly incorporating elastodynamic effects through Mach number dependence. These moving-load solutions serve as building blocks for constructing more general loading scenarios via linear superposition. Based on Green's functions, an inverse problem is formulated to reconstruct the unknown surface traction responsible for a given surface displacement. The inverse analysis is performed through a Fourier-domain inversion with regularization, which enables a direct and computationally efficient determination of the contact pressure without iterative forward simulations. This framework is applied to a rigid wheel-ground contact problem, where the imposed displacement is dictated by the wheel geometry. The reconstructed surface traction exhibits a smooth, symmetric distribution within the contact region, while the resulting subsurface stress fields are obtained in closed analytical form and involve dilogarithm functions. The principal stress difference reveals characteristic spatial patterns similar to photoelastic fringes, and their asymmetry increases with the Mach number, reflecting the dynamic nature of the moving contact. △ Less

Submitted 22 April, 2026; v1 submitted 19 January, 2026; originally announced January 2026.

Comments: 5 pages, 3 figures

Kinetic theory of dilute weakly charged granular gases with hard-core and inverse power-law interactions under uniform shear flow

Authors: Yuria Kobayashi, Makoto R. Kikuchi, Shunsuke Iizuka, Satoshi Takada

Abstract: We develop a kinetic-theory framework to investigate the steady rheology of a dilute gas interacting via a repulsive potential under uniform shear flow. Starting from the Boltzmann equation with a restitution coefficient that depends on the impact velocity and potential strength, we derive evolution equations for the stress tensor based on Grad's moment expansion. The resulting expressions for the… ▽ More We develop a kinetic-theory framework to investigate the steady rheology of a dilute gas interacting via a repulsive potential under uniform shear flow. Starting from the Boltzmann equation with a restitution coefficient that depends on the impact velocity and potential strength, we derive evolution equations for the stress tensor based on Grad's moment expansion. The resulting expressions for the collisional rates and transport coefficients are fitted with simple analytical functions that capture their temperature dependence over a wide range of shear rates. Comparison with direct simulation Monte Carlo (DSMC) results shows excellent quantitative agreement for the shear stress, temperature anisotropy, and shear viscosity. We also analyze the velocity distribution functions, revealing that the system remains nearly Maxwellian even under strong shear. △ Less

Submitted 24 February, 2026; v1 submitted 6 January, 2026; originally announced January 2026.

Comments: 10 pages, 10 figures

Journal ref: Eur. Phys. J. E 49, 34 (2026)

Observation of Shapiro Steps in the Charge Density Wave State Induced by Strain on a Piezoelectric Substrate

Authors: Koji Fujiwara, Takuya Kawada, Natsumi Nikaido, Jihoon Park, Nan Jiang, Shintaro Takada, Yasuhiro Niimi

Abstract: Recent development in nanotechnology has enabled us to investigate the dynamic properties of van der Waals materials on a piezoelectric substrate. Here we report on the dynamics of charge density wave (CDW) in NbSe$_{3}$ nanowires induced by surface acoustic waves (SAWs). Clear peaks in the differential resistance were observed at the resonant frequency of the SAW device. These peaks known as Shap… ▽ More Recent development in nanotechnology has enabled us to investigate the dynamic properties of van der Waals materials on a piezoelectric substrate. Here we report on the dynamics of charge density wave (CDW) in NbSe$_{3}$ nanowires induced by surface acoustic waves (SAWs). Clear peaks in the differential resistance were observed at the resonant frequency of the SAW device. These peaks known as Shapiro steps are typically observed by applying an rf current to NbSe$_{3}$ nanowires. We found that the Shapiro steps induced by SAWs show several distinct features from the ones induced by an rf current. Our detailed study revealed that a strain induced by SAWs plays a significant role in the Shapiro steps. The result clearly demonstrates the importance of the strain in CDW materials and paves the way for strain-induced device applications. △ Less

Submitted 12 November, 2025; originally announced November 2025.

Comments: 7 pages, 4 figures

Journal ref: Phys. Rev. Lett. 135, 256304 (2025)

Stress Analysis of a Square Elastic Body Under Biaxial Loading Using Airy Stress Functions

Authors: Ryu Suzuki, Shintaro Hokada, Satoshi Takada

Abstract: This study presents an analytical investigation of stress distributions in square-shaped elastic bodies subjected to concentrated compressive loads under uniaxial and biaxial conditions. By employing the Airy stress function method, we derive closed-form solutions that satisfy the governing biharmonic equation and the prescribed boundary conditions along the edges of the square domain. The stress… ▽ More This study presents an analytical investigation of stress distributions in square-shaped elastic bodies subjected to concentrated compressive loads under uniaxial and biaxial conditions. By employing the Airy stress function method, we derive closed-form solutions that satisfy the governing biharmonic equation and the prescribed boundary conditions along the edges of the square domain. The stress components are expressed as series expansions, with coefficients determined to enforce boundary constraints. In the uniaxial compression case, the resulting stress fields exhibit strong agreement with photoelastic fringe patterns previously observed in experimental studies. For biaxial loading, the solution represents a superposition of two orthogonal compression scenarios, producing spatial variations in the principal stress difference depending on the location within the domain. △ Less

Submitted 26 August, 2025; originally announced August 2025.

Comments: 19 pages, 8 figures

Proposal for fast computational method for Hertzian contact theory

Authors: Shintaro Hokada, Shunsuke Iizuka, Satoshi Takada

Abstract: Fast computational method for Hertzian contact theory is proposed. An incremental formula is introduced to calculate the ellipticity of the contact disk when two elastic bodies are in contact. This method can determine the ellipticity with good accuracy in a small number of iterations is reported. This method is also shown to be applicable from the case of a near perfect circle to the case where t… ▽ More Fast computational method for Hertzian contact theory is proposed. An incremental formula is introduced to calculate the ellipticity of the contact disk when two elastic bodies are in contact. This method can determine the ellipticity with good accuracy in a small number of iterations is reported. This method is also shown to be applicable from the case of a near perfect circle to the case where the major diameter is sufficiently long compared to the minor diameter. △ Less

Submitted 12 August, 2025; v1 submitted 9 August, 2025; originally announced August 2025.

Comments: 6 pages, 4 figures

Generation of a single-cycle surface acoustic wave pulse on LiNbO$_3$ for application to thin film materials

Authors: Koji Fujiwara, Shunsuke Ota, Tetsuo Kodera, Yuma Okazaki, Nobu-Hisa Kaneko, Nan Jiang, Yasuhiro Niimi, Shintaro Takada

Abstract: Surface acoustic wave (SAW) technology has been explored in thin-film materials to discover fundamental phenomena and to investigate their physical properties. It is used to excite and manipulate quasi-particles such as phonons or magnons, and can dynamically modulate the properties of the materials. In the field, SAWs are typically excited by a continuous wave at a resonant frequency. Recently, g… ▽ More Surface acoustic wave (SAW) technology has been explored in thin-film materials to discover fundamental phenomena and to investigate their physical properties. It is used to excite and manipulate quasi-particles such as phonons or magnons, and can dynamically modulate the properties of the materials. In the field, SAWs are typically excited by a continuous wave at a resonant frequency. Recently, generation of a single-cycle SAW pulse has been demonstrated on GaAs substrate. Such a SAW pulse provides a potential to access a single quasi-particle excitation and to investigate its dynamics by time-resolved measurements. On the other hand, to modulate and control the properties of thin film materials, it is generally required to generate high-intensity SAWs. In this work, we demonstrate the efficient generation of a SAW pulse using a chirp interdigital transducer (IDT) on LiNbO$_3$ substrate. We have fabricated chirp IDT devices with bandwidths from 0.5 GHz to 5.5 GHz. We also confirmed the generation of a SAW pulse with 0.3 ns FWHM (full width at half maximum) by performing time-resolved measurements. The conversion efficiency between input power and SAW on LiNbO$_3$ substrate is approximately 45 times larger than that on GaAs substrate. This enables us to generate a high-intensity SAW pulse, meeting the requirement for the modulation of thin films. Our results will expand the research in the field, such as spintronics and magnonics, and lead to their further advancements. △ Less

Submitted 3 July, 2025; originally announced July 2025.

Comments: 7 pages, 4 figures

Journal ref: Appl. Phys. Lett. 127, 022406 (2025)

Stress distribution in elastic disks with a hole under uniaxial compression

Authors: Ken Okamura, Yosuke Sato, Satoshi Takada

Abstract: This paper investigates the stress and displacement distribution in a two-dimensional elastic hollow disk subjected to distributed diametric loading, extending our previous analysis of concentrated loading [Okamura et al. Strength Mater. 57, 102-114 (2025)]. The study provides deeper insights into the mechanical behavior of materials such as concrete and rock by examining the effects of load distr… ▽ More This paper investigates the stress and displacement distribution in a two-dimensional elastic hollow disk subjected to distributed diametric loading, extending our previous analysis of concentrated loading [Okamura et al. Strength Mater. 57, 102-114 (2025)]. The study provides deeper insights into the mechanical behavior of materials such as concrete and rock by examining the effects of load distribution on stress localization and displacement patterns. Using elastodynamic theory, we derive the static stress distributions and identify key differences from the concentrated loading case, particularly in the locations and magnitudes of stress extrema. This work contributes to a more comprehensive understanding of stress behavior in elastic disks under realistic loading conditions. △ Less

Submitted 28 May, 2025; originally announced May 2025.

Comments: 4 pages, 3 figures, Powders & Grains 2025

Spin phase detection by spin current in a chiral helimagnet

Authors: Nan Jiang, Shota Suzuki, Issei Sasaki, Kazuki Yamada, Ryoma Kawahara, Shintaro Takada, Yusuke Shimamoto, Hiroki Shoji, Yusuke Kousaka, Jun-ichiro Ohe, Yoshihiko Togawa, Yasuhiro Niimi

Abstract: Helimagnets, characterized by a helical arrangement of magnetic moments, possess unique internal degrees of freedom, including the spin phase, defined by the phase of the helical magnetic structure. Electrical detection of the spin phase is essential for both practical applications and fundamental research in helimagnets. Here, we demonstrate the electrical detection of the spin phase in a van der… ▽ More Helimagnets, characterized by a helical arrangement of magnetic moments, possess unique internal degrees of freedom, including the spin phase, defined by the phase of the helical magnetic structure. Electrical detection of the spin phase is essential for both practical applications and fundamental research in helimagnets. Here, we demonstrate the electrical detection of the spin phase in a van der Waals nanoscale chiral helimagnet CrNb$_3$S$_6$ using nonlocal spin valve measurements. Due to the short spin diffusion length in CrNb$_3$S$_6$ ($\sim5$~nm), the surface magnetic moment direction, which corresponds to the spin phase, can be detected via spin currents. The experimentally observed magnetic field dependence of the nonlocal spin valve signal is consistent with that of the surface magnetic moment in the helical magnetic structure, as supported by micromagnetic simulations. Our results establish spin currents as a powerful tool for detecting the spin phase in helimagnets, opening avenues for utilizing the spin phase as a novel internal degree of freedom in nanoscale spintronic devices. △ Less

Submitted 14 May, 2025; originally announced May 2025.

Comments: 15 pages, 9 figures

Displacement and Stress Analysis of an Elastic Hollow Disk: Comparison with Strength of Materials' Prediction

Authors: Ken Okamura, Yosuke Sato, Satoshi Takada

Abstract: This paper analyzes the stress distribution in a two-dimensional elastic disk under diametric loading, with a focus on enhancing the understanding of concrete and rock materials' mechanical behavior. The study revisits the Brazilian test and addresses its high shear stress issue near loading points by exploring the ring test, which introduces a central hole in the disk. Using dynamic elasticity th… ▽ More This paper analyzes the stress distribution in a two-dimensional elastic disk under diametric loading, with a focus on enhancing the understanding of concrete and rock materials' mechanical behavior. The study revisits the Brazilian test and addresses its high shear stress issue near loading points by exploring the ring test, which introduces a central hole in the disk. Using dynamic elasticity theory, we derive stress distributions over time and extend the analysis to static conditions. This approach distinguishes between longitudinal and transverse wave effects, providing a detailed stress field analysis. By drawing parallels with curved beam theories, we demonstrate the applicability of dynamic elasticity theory to complex stress problems, offering improved insights into the stress behavior in elastic disks. △ Less

Submitted 6 May, 2025; originally announced May 2025.

Comments: 11 pages, 4 figures

Rheology of dilute granular gases with hard-core and inverse power-law potentials

Authors: Yuria Kobayashi, Shunsuke Iizuka, Satoshi Takada

Abstract: The kinetic theory of dilute granular gases with hard-core and inverse power-law potentials is developed. The scattering process is studied theoretically, which yields the relative speed and the impact parameter dependence of the scattering angle. The viscosity is derived from the Boltzmann equation and its temperature dependence is plotted. We also perform the direct simulation Monte Carlo to che… ▽ More The kinetic theory of dilute granular gases with hard-core and inverse power-law potentials is developed. The scattering process is studied theoretically, which yields the relative speed and the impact parameter dependence of the scattering angle. The viscosity is derived from the Boltzmann equation and its temperature dependence is plotted. We also perform the direct simulation Monte Carlo to check the validity of the theory. △ Less

Submitted 1 May, 2025; v1 submitted 17 April, 2025; originally announced April 2025.

Comments: 4 pages, 4 figures

Eigenstate control of plasmon wavepackets with electron-channel blockade

Authors: Shintaro Takada, Giorgos Georgiou, Junliang Wang, Yuma Okazaki, Shuji Nakamura, David Pomaranski, Arne Ludwig, Andreas D. Wieck, Michihisa Yamamoto, Christopher Bäuerle, Nobu-Hisa Kaneko

Abstract: Coherent manipulation of plasmon wavepackets in solid-state systems is crucial for advancing nanoscale electronic devices, offering a unique platform for quantum information processing based on propagating quantum bits. Controlling the eigenstate of plasmon wavepackets is essential, as it determines its propagation speed and hence the number of quantum operations that can be performed during its f… ▽ More Coherent manipulation of plasmon wavepackets in solid-state systems is crucial for advancing nanoscale electronic devices, offering a unique platform for quantum information processing based on propagating quantum bits. Controlling the eigenstate of plasmon wavepackets is essential, as it determines its propagation speed and hence the number of quantum operations that can be performed during its flight-time through a quantum system. When plasmon wavepackets are generated by short voltage pulses and transmitted through nanoscale devices, they distribute among multiple electron conduction channels via Coulomb interactions, a phenomenon known as charge fractionalisation. This spreading complicates plasmon manipulation in quantum circuits and makes precise control of the eigenstates of plasmon wavepackets challenging. Using a cavity, we demonstrate the ability to isolate and select electron conduction channels contributing to plasmon excitation, thus enabling precise control of plasmon eigenstate. Specifically, we observe an electron-channel blockade effect, where charge fractionalisation into cavity-confined channels is suppressed due to the plasmon's narrow energy distribution, enabling more stable and predictable plasmonic circuits. This technique provides a versatile tool for designing plasmonic circuits, offering the ability to tailor plasmon speed through local parameters, minimise unwanted plasmon excitation in adjacent circuits, and enable the precise selection of electron-channel plasmon eigenstates in quantum interferometers. △ Less

Submitted 22 November, 2025; v1 submitted 9 March, 2025; originally announced March 2025.

Comments: 24 pages, 5 figures, 7 supplementary figures

Journal ref: Nature Communications 16, 9942 (2025)

Fermion Casimir effect and magnetic Larkin-Ovchinnikov phases

Authors: Antonino Flachi, Muneto Nitta, Satoshi Takada, Ryosuke Yoshii

Abstract: This paper explores how magnetic fields affect the Casimir effect within the context of a simple quasi-1D interacting fermionic system. A novel phenomenon emerges, resulting from the interaction between external magnetic fields and boundary conditions, which alters the ground state in complex ways and leads to first-order phase transitions among various ground states, specifically inhomogeneous so… ▽ More This paper explores how magnetic fields affect the Casimir effect within the context of a simple quasi-1D interacting fermionic system. A novel phenomenon emerges, resulting from the interaction between external magnetic fields and boundary conditions, which alters the ground state in complex ways and leads to first-order phase transitions among various ground states, specifically inhomogeneous solutions with differing node counts. We calculate the Casimir force, which exhibits discontinuities (jumps) at the transition points between the different ground states. △ Less

Submitted 24 October, 2024; originally announced October 2024.

Comments: 6 pages, 5 figures

Semiconductor Circuits for Quantum Computing with Electronic Wave Packets

Authors: David Pomaranski, Ryo Ito, Ngoc Han Tu, Arne Ludwig, Andreas D. Wieck, Shintaro Takada, Nobu-Hisa Kaneko, Seddik Ouacel, Christopher Bauerle, Michihisa Yamamoto

Abstract: Standard approaches to quantum computing require significant overhead to correct for errors. The hardware size for conventional quantum processors in solids often increases linearly with the number of physical qubits, such as for transmon qubits in superconducting circuits or electron spin qubits in quantum dot arrays. While photonic circuits based on flying qubits do not suffer from decoherence o… ▽ More Standard approaches to quantum computing require significant overhead to correct for errors. The hardware size for conventional quantum processors in solids often increases linearly with the number of physical qubits, such as for transmon qubits in superconducting circuits or electron spin qubits in quantum dot arrays. While photonic circuits based on flying qubits do not suffer from decoherence or lack of potential scalability, they have encountered significant challenges to overcome photon loss in long delay circuits. Here, we propose an alternative approach that utilizes flying electronic wave packets propagating in solid-state quantum semiconductor circuits. Using a novel time-bin architecture for the electronic wave packets, hardware requirements are drastically reduced because qubits can be created on-demand and manipulated with a common hardware element, unlike the localized approach of wiring each qubit individually. The electronic Coulomb interaction enables reliable coupling and readout of qubits. Improving upon previous devices, we realize electronic interference at the level of a single quantized mode that can be used for manipulation of electronic wavepackets. This important landmark lays the foundation for fault-tolerant quantum computing with a compact and scalable architecture based on electron interferometry in semiconductors. △ Less

Submitted 21 October, 2024; originally announced October 2024.

Electronic interferometry with ultrashort plasmonic pulses

Authors: Seddik Ouacel, Lucas Mazzella, Thomas Kloss, Matteo Aluffi, Thomas Vasselon, Hermann Edlbauer, Junliang Wang, Clement Geffroy, Jashwanth Shaju, Arne Ludwig, Andreas D. Wieck, Michihisa Yamamoto, David Pomaranski, Shintaro Takada, Nobu-Hisa Kaneko, Giorgos Georgiou, Xavier Waintal, Matias Urdampilleta, Hermann Sellier, Christopher Bäuerle

Abstract: Electronic flying qubits offer an interesting alternative to photonic qubits: electrons propagate slower, hence easier to control in real time, and Coulomb interaction enables direct entanglement between different qubits. Although their coherence time is limited, flying electrons in the form of picosecond plasmonic pulses could be competitive in terms of the number of achievable coherent operation… ▽ More Electronic flying qubits offer an interesting alternative to photonic qubits: electrons propagate slower, hence easier to control in real time, and Coulomb interaction enables direct entanglement between different qubits. Although their coherence time is limited, flying electrons in the form of picosecond plasmonic pulses could be competitive in terms of the number of achievable coherent operations. The key challenge in achieving this critical milestone is the development of a new technology capable of injecting 'on-demand' single-electron wavepackets into quantum devices, with temporal durations comparable to or shorter than the device dimensions. Here, we take a significant step towards achieving this regime in a quantum nanoelectronic system by injecting ultrashort single-electron plasmonic pulses into a 14-micrometer-long Mach-Zehnder interferometer. Our results establish that quantum coherence is robust under the on-demand injection of ultrashort plasmonic pulses, as evidenced by the observation of coherent oscillations in the single-electron regime. Building on this, our results demonstrate for the first time the existence of a new "non-adiabatic" regime that is prominent at high frequencies. This breakthrough highlights the potential of flying qubits as a promising alternative to localised qubit architectures, offering advantages such as a reduced hardware footprint, enhanced connectivity, and scalability for quantum information processing. △ Less

Submitted 5 January, 2025; v1 submitted 23 August, 2024; originally announced August 2024.

Kinetic theory of dilute granular gases having an inverse power law potential

Authors: Satoshi Takada

Abstract: The kinetic theory of dilute granular gases having an inverse power law repulsive potential is studied. We derive the time evolution of the temperature and the transport coefficients from the Boltzmann equation. We also investigate the linear stability analysis of the hydrodynamics, and study the softness dependence of the thresholds for the shear and heat modes against the restitution coefficient… ▽ More The kinetic theory of dilute granular gases having an inverse power law repulsive potential is studied. We derive the time evolution of the temperature and the transport coefficients from the Boltzmann equation. We also investigate the linear stability analysis of the hydrodynamics, and study the softness dependence of the thresholds for the shear and heat modes against the restitution coefficient. △ Less

Submitted 25 August, 2026; v1 submitted 16 June, 2024; originally announced June 2024.

Comments: 12 pages, 8 figures. The original manuscript was written in 2016

Electron qubits surfing on acoustic waves: review of recent progress

Authors: Junliang Wang, Hermann Edlbauer, Baptiste Jadot, Tristan Meunier, Shintaro Takada, Christopher Bäuerle, Hermann Sellier

Abstract: The displacement of a single electron enables exciting avenues for nanotechnology with vast application potential in quantum metrology, quantum communication and quantum computation. Surface acoustic waves (SAW) have proven itself as a surprisingly useful solution to perform this task over large distance with outstanding precision and reliability. Over the last decade, important milestones have be… ▽ More The displacement of a single electron enables exciting avenues for nanotechnology with vast application potential in quantum metrology, quantum communication and quantum computation. Surface acoustic waves (SAW) have proven itself as a surprisingly useful solution to perform this task over large distance with outstanding precision and reliability. Over the last decade, important milestones have been achieved bringing SAW-driven single-electron transport from first proof-of-principle demonstrations to accurate, highly-controlled implementations, such as coherent spin transport, charge-to-photon conversion, or antibunching of charge states. Beyond the well-established piezoelectric gallium-arsenide platform, first realisations of acousto-electronic transport have also been carried out on the surface of liquid helium that promises unique stability and coherence. In this review article, we aim to keep track of this remarkable progress in SAW-driven transport of electron qubits by explaining these recent achievements from basic principles, with an outlook on follow-up experiments and near-term applications. △ Less

Submitted 13 November, 2025; v1 submitted 7 February, 2024; originally announced February 2024.

Journal ref: J. Phys. D: Appl. Phys. 58, 023002 (2025)

Revisiting stress propagation in a two-dimensional elastic circular disk under diametric loading

Authors: Yosuke Sato, Haruto Ishikawa, Satoshi Takada

Abstract: In this paper, we present a comprehensive investigation of stress propagation in a two-dimensional elastic circular disk. To accurately describe the displacements and stress fields within the disk, we employ a scalar and vector potential approach, representing them as sums of Bessel functions. The determination of the coefficients for these expansions is accomplished in the Laplace space, where we… ▽ More In this paper, we present a comprehensive investigation of stress propagation in a two-dimensional elastic circular disk. To accurately describe the displacements and stress fields within the disk, we employ a scalar and vector potential approach, representing them as sums of Bessel functions. The determination of the coefficients for these expansions is accomplished in the Laplace space, where we compare the boundary conditions. By converting the inverse Laplace transforms into complex integrals using residue calculus, we successfully derive explicit expressions for the displacements and stress fields. Notably, these expressions encompass primary, secondary, and surface waves, providing a thorough characterization of the stress propagation phenomena within the disk. Our findings contribute to the understanding of mechanical behavior in disk-shaped components and can be valuable in the design and optimization of such structures across various engineering disciplines. △ Less

Submitted 29 December, 2023; originally announced January 2024.

Comments: 23 pages, 9 figures

Suppression of Electromagnetic Crosstalk by Differential Excitation for SAW Generation

Authors: Shunsuke Ota, Yuma Okazaki, Shuji Nakamura, Takehiko Oe, Hermann Sellier, Christopher Bäuerle, Nobu-Hisa Kaneko, Tetsuo Kodera, Shintaro Takada

Abstract: Surface acoustic waves (SAWs) hold a vast potential in various fields such as spintronics, quantum acoustics, and electron-quantum optics, but an electromagnetic wave emanating from SAW generation circuits has often been a major hurdle. Here, we investigate a differential excitation method of interdigital transducers (IDTs) to generate SAWs while reducing the electromagnetic wave. The results show… ▽ More Surface acoustic waves (SAWs) hold a vast potential in various fields such as spintronics, quantum acoustics, and electron-quantum optics, but an electromagnetic wave emanating from SAW generation circuits has often been a major hurdle. Here, we investigate a differential excitation method of interdigital transducers (IDTs) to generate SAWs while reducing the electromagnetic wave. The results show that electromagnetic waves are suppressed by more than 90% in all directions. This suppression overcomes the operating limits and improves the scalability of SAW systems. Our results promise to facilitate the development of SAW-based applications in a wide range of research fields. △ Less

Submitted 24 December, 2023; originally announced December 2023.

Journal ref: Appl. Phys. Express 17 022002 (2024)

On-Demand Single-Electron Source via Single-Cycle Acoustic Pulses

Authors: Shunsuke Ota, Junliang Wang, Hermann Edlbauer, Yuma Okazaki, Shuji Nakamura, Takehiko Oe, Arne Ludwig, Andreas D. Wieck, Hermann Sellier, Christopher Bäuerle, Nobu-Hisa Kaneko, Tetsuo Kodera, Shintaro Takada

Abstract: Surface acoustic waves (SAWs) are a reliable solution to transport single electrons with precision in piezoelectric semiconductor devices. Recently, highly efficient single-electron transport with a strongly compressed single-cycle acoustic pulse has been demonstrated. This approach, however, requires surface gates constituting the quantum dots, their wiring, and multiple gate movements to load an… ▽ More Surface acoustic waves (SAWs) are a reliable solution to transport single electrons with precision in piezoelectric semiconductor devices. Recently, highly efficient single-electron transport with a strongly compressed single-cycle acoustic pulse has been demonstrated. This approach, however, requires surface gates constituting the quantum dots, their wiring, and multiple gate movements to load and unload the electrons, which is very time-consuming. Here, on the contrary, we employ such a single-cycle acoustic pulse in a much simpler way - without any quantum dot at the entrance or exit of a transport channel - to perform single-electron transport between distant electron reservoirs. We observe the transport of a solitary electron in a single-cycle acoustic pulse via the appearance of the quantized acousto-electric current. The simplicity of our approach allows for on-demand electron emission with arbitrary delays on a ns time scale. We anticipate that enhanced synthesis of the SAWs will facilitate electron-quantum-optics experiments with multiple electron flying qubits. △ Less

Submitted 30 November, 2023; originally announced December 2023.

Journal ref: Phys. Rev. Applied 21, 024034 (2024)

Multiple quantum Mpemba effect: exceptional points and oscillations

Authors: Amit Kumar Chatterjee, Satoshi Takada, Hisao Hayakawa

Abstract: We explore the role of exceptional points and complex eigenvalues on the occurrence of the quantum Mpemba effect. To this end, we study a two-level driven dissipative system subjected to an oscillatory electric field and dissipative coupling with the environment. We find that both exceptional points and complex eigenvalues can lead to $multiple$ quantum Mpemba effect. It occurs in an observable wh… ▽ More We explore the role of exceptional points and complex eigenvalues on the occurrence of the quantum Mpemba effect. To this end, we study a two-level driven dissipative system subjected to an oscillatory electric field and dissipative coupling with the environment. We find that both exceptional points and complex eigenvalues can lead to $multiple$ quantum Mpemba effect. It occurs in an observable when time evolved copies corresponding to two different initial conditions, one initially having higher observable value compared to the other and both relaxing towards the same steady state, intersect each other more than once during their relaxation process. Each of the intersections denotes a quantum Mpemba effect and marks the reversal of identities between the two copies i.e. the copy with higher observable value before the intersection becomes the lower valued copy (and vice versa) after the intersection. Such multiple intersections originate from additional algebraic time dependence at the exceptional points and due to oscillatory relaxation in the case of complex eigenvalues. We provide analytical results for quantum Mpemba effect in the density matrix in presence of coherence. Depending on the control parameters (drive and dissipation), observables such as energy, von Neumann entropy, temperature etc. exhibit either single or multiple quantum Mpemba effect. However, the distance from steady state measured in terms of the Kullback-Leibler divergence shows only single quantum Mpemba effect although the corresponding speed gives rise to either single or multiple quantum Mpemba effect. △ Less

Submitted 13 September, 2024; v1 submitted 2 November, 2023; originally announced November 2023.

Comments: 24 pages, 18 figures, published version

Journal ref: Phys. Rev. A 110, 022213 (2024)

Quantum Mpemba effect in a quantum dot with reservoirs

Authors: Amit Kumar Chatterjee, Satoshi Takada, Hisao Hayakawa

Abstract: We demonstrate the quantum Mpemba effect in a quantum dot coupled to two reservoirs, described by the Anderson model. We show that the system temperatures starting from two different initial values (hot and cold), cross each other at finite time (and thereby reverse their identities i.e. hot becomes cold and vice versa) to generate thermal quantam Mpemba effect. The slowest relaxation mode believe… ▽ More We demonstrate the quantum Mpemba effect in a quantum dot coupled to two reservoirs, described by the Anderson model. We show that the system temperatures starting from two different initial values (hot and cold), cross each other at finite time (and thereby reverse their identities i.e. hot becomes cold and vice versa) to generate thermal quantam Mpemba effect. The slowest relaxation mode believed to play the dominating role in Mpemba effect in Markovian systems, does not contribute to such anomalous relaxation in the present model. In this connection, our analytical result provides necessary condition for producing quantum Mpemba effect in the density matrix elements of the quantum dot, as a combined effect of the remaining relaxation modes. △ Less

Submitted 13 July, 2023; v1 submitted 5 April, 2023; originally announced April 2023.

Comments: 14 pages, 9 figures

Journal ref: Phys. Rev. Lett. 131, 080402 (2023)

Rheology of dilute granular gas mixtures where the grains interact via a square shoulder and well potential

Authors: Kiwamu Yoshii, Satoshi Takada, Kosuke Kurosawa, Thorsten Pöschel

Abstract: We develop the rheology of a dilute granular gas mixture. Motivated by the interaction of charged granular particles, we assume that the grains interact via a square shoulder and well potential. Employing kinetic theory, we compute the temperature and the shear viscosity as functions of the shear rate. Numerical simulations confirm our results above the critical shear rate. At a shear rate below a… ▽ More We develop the rheology of a dilute granular gas mixture. Motivated by the interaction of charged granular particles, we assume that the grains interact via a square shoulder and well potential. Employing kinetic theory, we compute the temperature and the shear viscosity as functions of the shear rate. Numerical simulations confirm our results above the critical shear rate. At a shear rate below a critical value, clustering of the particles occurs. △ Less

Submitted 16 December, 2022; originally announced December 2022.

Comments: 12 pages, 14 figures

Coulomb-mediated antibunching of an electron pair surfing on sound

Authors: Junliang Wang, Hermann Edlbauer, Aymeric Richard, Shunsuke Ota, Wanki Park, Jeongmin Shim, Arne Ludwig, Andreas Wieck, Heung-Sun Sim, Matias Urdampilleta, Tristan Meunier, Tetsuo Kodera, Nobu-Hisa Kaneko, Hermann Sellier, Xavier Waintal, Shintaro Takada, Christopher Bäuerle

Abstract: Electron flying qubits are envisioned as potential information link within a quantum computer, but also promise -- alike photonic approaches -- a self-standing quantum processing unit. In contrast to its photonic counterpart, electron-quantum-optics implementations are subject to Coulomb interaction, which provide a direct route to entangle the orbital or spin degree of freedom. However, the contr… ▽ More Electron flying qubits are envisioned as potential information link within a quantum computer, but also promise -- alike photonic approaches -- a self-standing quantum processing unit. In contrast to its photonic counterpart, electron-quantum-optics implementations are subject to Coulomb interaction, which provide a direct route to entangle the orbital or spin degree of freedom. However, the controlled interaction of flying electrons at the single particle level has not yet been established experimentally. Here we report antibunching of a pair of single electrons that is synchronously shuttled through a circuit of coupled quantum rails by means of a surface acoustic wave. The in-flight partitioning process exhibits a reciprocal gating effect which allows us to ascribe the observed repulsion predominantly to Coulomb interaction. Our single-shot experiment marks an important milestone on the route to realise a controlled-phase gate for in-flight quantum manipulations. △ Less

Submitted 7 October, 2022; originally announced October 2022.

Journal ref: Nature Nanotechnology 18, 721-726 (2023)

Generation of a single-cycle acoustic pulse: a scalable solution for transport in single-electron circuits

Authors: Junliang Wang, Shunsuke Ota, Hermann Edlbauer, Baptiste Jadot, Pierre-André Mortemousque, Aymeric Richard, Yuma Okazaki, Shuji Nakamura, Arne Ludwig, Andreas D. Wieck, Matias Urdampilleta, Tristan Meunier, Tetsuo Kodera, Nobu-Hisa Kaneko, Shintaro Takada, Christopher Bäuerle

Abstract: The synthesis of single-cycle, compressed optical and microwave pulses sparked novel areas of fundamental research. In the field of acoustics, however, such a generation has not been introduced yet. For numerous applications, the large spatial extent of surface acoustic waves (SAW) causes unwanted perturbations and limits the accuracy of physical manipulations. Particularly, this restriction appli… ▽ More The synthesis of single-cycle, compressed optical and microwave pulses sparked novel areas of fundamental research. In the field of acoustics, however, such a generation has not been introduced yet. For numerous applications, the large spatial extent of surface acoustic waves (SAW) causes unwanted perturbations and limits the accuracy of physical manipulations. Particularly, this restriction applies to SAW-driven quantum experiments with single flying electrons, where extra modulation renders the exact position of the transported electron ambiguous and leads to undesired spin mixing. Here, we address this challenge by demonstrating single-shot chirp synthesis of a strongly compressed acoustic pulse. Employing this solitary SAW pulse to transport a single electron between distant quantum dots with an efficiency exceeding 99%, we show that chirp synthesis is competitive with regular transduction approaches. Performing a time-resolved investigation of the SAW-driven sending process, we outline the potential of the chirped SAW pulse to synchronize single-electron transport from many quantum-dot sources. By superimposing multiple pulses, we further point out the capability of chirp synthesis to generate arbitrary acoustic waveforms tailorable to a variety of (opto)nanomechanical applications. Our results shift the paradigm of compressed pulses to the field of acoustic phonons and pave the way for a SAW-driven platform of single-electron transport that is precise, synchronized, and scalable. △ Less

Submitted 31 July, 2022; originally announced August 2022.

Comments: To be published in Physical Review X

Journal ref: Phys. Rev. X 12, 031035 (2022)

Kinetic theory of discontinuous shear thickening of a moderately dense inertial suspension of frictionless soft particles

Authors: Satoshi Takada, Kazuhiro Hara, Hisao Hayakawa

Abstract: We demonstrate that a discontinuous shear thickening (DST) can take place even in a moderately dense inertial suspension consisting of frictionless soft particles. This DST can be regarded as an ignited-quenched transition in the inertial suspension. An approximate kinetic theory well recovers the results of the Langevin simulation in the wide range of the volume fraction without any fitting param… ▽ More We demonstrate that a discontinuous shear thickening (DST) can take place even in a moderately dense inertial suspension consisting of frictionless soft particles. This DST can be regarded as an ignited-quenched transition in the inertial suspension. An approximate kinetic theory well recovers the results of the Langevin simulation in the wide range of the volume fraction without any fitting parameters. △ Less

Submitted 14 January, 2025; v1 submitted 12 July, 2022; originally announced July 2022.

Comments: 41 pages, 21 figures, 3 tables

Journal ref: Prog. Theor. Exp. Phys. 2025, 023J01 (2025)

Discontinuous shear thickening of a moderately dense inertial suspension of hydrodynamically interacting frictionless soft particles

Authors: Satoshi Takada, Kazuhiro Hara, Hisao Hayakawa

Abstract: We demonstrate that discontinuous shear thickening (DST) can occur even in moderately dense, inertial suspensions of hydrodynamically interacting, frictionless soft particles. Using the Lubrication-Friction Discrete Element Method, our simulations reveal that DST can emerge at lower particle densities, provided that both the inertia of the suspended particles and their softness are sufficiently pr… ▽ More We demonstrate that discontinuous shear thickening (DST) can occur even in moderately dense, inertial suspensions of hydrodynamically interacting, frictionless soft particles. Using the Lubrication-Friction Discrete Element Method, our simulations reveal that DST can emerge at lower particle densities, provided that both the inertia of the suspended particles and their softness are sufficiently pronounced. Furthermore, we show that, under these conditions, the DST behavior obtained from the simulation qualitatively agrees with that predicted by kinetic theory, even without accounting for hydrodynamic interactions. These findings expand the understanding of DST in soft particle systems and highlight the importance of particle inertia and softness in controlling rheological behavior. △ Less

Submitted 26 May, 2025; v1 submitted 12 July, 2022; originally announced July 2022.

Comments: 4 pages, 2 figures. Accepted in the Proceedings of Powders & Grains 2025

Drag of an elliptic intruder in a two-dimensional granular environment

Authors: Takumi Kubota, Haruto Ishikawa, Satoshi Takada

Abstract: The drag of an elliptic intruder in a two-dimensional granular environment is numerically studied. The movement parallel to the major axis of the intruder is found to be unstable. The drag law is given by the sum of the yield force and the dynamic term, the latter of which is approximately reproduced by a simple collision model. The flow field around the intruder for sufficiently larger drag force… ▽ More The drag of an elliptic intruder in a two-dimensional granular environment is numerically studied. The movement parallel to the major axis of the intruder is found to be unstable. The drag law is given by the sum of the yield force and the dynamic term, the latter of which is approximately reproduced by a simple collision model. The flow field around the intruder for sufficiently larger drag force is well fitted by the streamlines obtained from the perfect fluid. The stress fields around the intruder are also investigated when the movement of the intruder is balanced with interactions with the surrounding particles. The Airy stress function is found to well reproduce the stress fields once the stress on the surface of the intruder is given. △ Less

Submitted 14 June, 2022; originally announced June 2022.

Comments: 17 pages, 8 figures

Magnetism of Al$_x$Fe$_{2-x}$GeO$_5$ with Andalusite Structure

Authors: K. Kakimoto, S. Takada, H. Ohta, Y. Haraguchi, M. Hagihala, S. Torii, T. Kamiyama, H. Mitamura, M. Tokunaga, A. Hatakeyama, H. Aruga Katori

Abstract: The magnetism of Al$_x$Fe$_{2-x}$GeO$_5$ from $x$ = 0.09 to $x$ = 0.91 with andalusite structure was examined. The magnetic properties of Al$_x$Fe$_{2-x}$GeO$_5$ at low temperatures were found to be weak ferromagnetic-like state for $x$ $<$ 0.3 and spin-glass state for $x$ $>$ 0.3. The small spontaneous magnetization that appears in the weak ferromagnetic-like phase would be due to the presence of… ▽ More The magnetism of Al$_x$Fe$_{2-x}$GeO$_5$ from $x$ = 0.09 to $x$ = 0.91 with andalusite structure was examined. The magnetic properties of Al$_x$Fe$_{2-x}$GeO$_5$ at low temperatures were found to be weak ferromagnetic-like state for $x$ $<$ 0.3 and spin-glass state for $x$ $>$ 0.3. The small spontaneous magnetization that appears in the weak ferromagnetic-like phase would be due to the presence of Dzyaloshinsky-Moriya interaction or to the difference in the magnitude of the magnetic moment of Fe$^{3+}$ in the octahedral and trigonal bipyramidal sites. The appearance of the spin-glass phase indicates that the dilution of Fe ions by Al ions in Al$_x$Fe$_{2-x}$GeO$_5$ causes the competition between ferromagnetic and antiferromagnetic interactions. The $x$ dependence of the site occupancy of Fe ions suggests that Fe$_2$GeO$_5$ with andalusite structure cannot be synthesized. △ Less

Submitted 3 February, 2022; originally announced February 2022.

Comments: 19 pages, 14 figure

Journal ref: J. Phys. Soc. Jpn. 91 054704 (2022)

Rheology of a dilute binary mixture of inertial suspension under simple shear flow

Authors: Satoshi Takada, Hisao Hayakawa, Vicente Garzó

Abstract: The rheology of a dilute binary mixture of inertial suspension under simple shear flow is analyzed in the context of the Boltzmann kinetic equation. The effect of the surrounding viscous gas on the solid particles is accounted for by means of a deterministic viscous drag force plus a stochastic Langevin-like term defined in terms of the environmental temperature $T_\text{env}$. Grad's moment metho… ▽ More The rheology of a dilute binary mixture of inertial suspension under simple shear flow is analyzed in the context of the Boltzmann kinetic equation. The effect of the surrounding viscous gas on the solid particles is accounted for by means of a deterministic viscous drag force plus a stochastic Langevin-like term defined in terms of the environmental temperature $T_\text{env}$. Grad's moment method is employed to determine the temperature ratio and the pressure tensor in terms of the coefficients of restitution, concentration, the masses and diameters of the components of the mixture, and the environmental temperature. Analytical results are compared against event-driven Langevin simulations for mixtures of hard spheres with the same mass density $m_1/m_2=(σ^{(1)}/σ^{(2)})^3$, $m_i$ and $σ^{(1)}$ being the mass and diameter, respectively, of the species $i$. It is confirmed that the theoretical predictions agree with simulations of various size ratios $σ^{(1)}/σ^{(2)}$ and for elastic and inelastic collisions in the wide range of parameters' space. It is remarkable that the temperature ratio $T_1/T_2$ and the viscosity ratio $η_1/η_2$ ($η_i$ being the partial contribution of the species $i$ to the total shear viscosity $η=η_1+η_2$) discontinuously change at a certain shear rate as the size ratio increases; this feature (which is expected to occur in the thermodynamic limit) cannot be completely captured by simulations due to small system size. In addition, a Bhatnagar--Gross--Krook (BGK)-type kinetic model adapted to mixtures of inelastic hard spheres is exactly solved when $T_\text{env}$ is much smaller than the kinetic temperature $T$. A comparison between the velocity distribution functions obtained from Grad's method, BGK model, and simulations is carried out. △ Less

Submitted 1 September, 2023; v1 submitted 22 July, 2021; originally announced July 2021.

Comments: 39 pages, 22 figures

Journal ref: Prog. Theor. Exp. Phys. 2023, ptad126 (2023)

In-flight distribution of an electron within a surface acoustic wave

Authors: Hermann Edlbauer, Junliang Wang, Shunsuke Ota, Americ Richard, Baptiste Jadot, Pierre-André Mortemousque, Yuma Okazaki, Shuji Nakamura, Tetsuo Kodera, Nobu-Hisa Kaneko, Arne Ludwig, Andreas D. Wieck, Matias Urdampilleta, Tristan Meunier, Christopher Bäuerle, Shintaro Takada

Abstract: Surface acoustic waves (SAW) have large potential to realize quantum-optics-like experiments with single flying electrons employing their spin or charge degree of freedom. For such quantum applications, highly efficient trapping of the electron in a specific moving quantum dot (QD) of a SAW train plays a key role. Probabilistic transport over multiple moving minima would cause uncertainty in synch… ▽ More Surface acoustic waves (SAW) have large potential to realize quantum-optics-like experiments with single flying electrons employing their spin or charge degree of freedom. For such quantum applications, highly efficient trapping of the electron in a specific moving quantum dot (QD) of a SAW train plays a key role. Probabilistic transport over multiple moving minima would cause uncertainty in synchronisation that is detrimental for coherence of entangled flying electrons and in-flight quantum operations. It is thus of central importance to identify the device parameters enabling electron transport within a single SAW minimum. A detailed experimental investigation of this aspect is so far missing. Here we fill this gap by demonstrating time-of-flight measurements for a single electron that is transported via a SAW train between distant stationary QDs. Our measurements reveal the in-flight distribution of the electron within the moving acousto-electric quantum dots of the SAW train. Increasing the acousto-electric amplitude, we observe the threshold necessary to confine the flying electron at a specific, deliberately chosen SAW minimum. Investigating the effect of a barrier along the transport channel, we also benchmark the robustness of SAW-driven electron transport against stationary potential variations. Our results pave the way for highly controlled transport of electron qubits in a SAW-driven platform for quantum experiments. △ Less

Submitted 24 September, 2021; v1 submitted 20 July, 2021; originally announced July 2021.

Comments: Main paper: 11 pages, 3 figures, Supplementary material: 5 pages, 4 figures

Journal ref: Appl. Phys. Lett. 119, 114004 (2021)

Heat-Driven Electron-Motion in a Nanoscale Electronic Circuit

Authors: Shintaro Takada, Giorgos Georgiou, Everton Arrighi, Hermann Edlbauer, Yuma Okazaki, Shuji Nakamura, Arne Ludwig, Andreas D. Wieck, Michihisa Yamamoto, Christopher Bäuerle, Nobu-Hisa Kaneko

Abstract: We study the interaction between two closely spaced but electrically isolated quasi-one-dimensional electrical wires by a drag experiment. In this work we experimentally demonstrate the generation of current in an unbiased (drag) wire, which results from the interactions with a neighboring biased (drive) wire. The direction of the drag current depends on the length of the one-dimensional wire with… ▽ More We study the interaction between two closely spaced but electrically isolated quasi-one-dimensional electrical wires by a drag experiment. In this work we experimentally demonstrate the generation of current in an unbiased (drag) wire, which results from the interactions with a neighboring biased (drive) wire. The direction of the drag current depends on the length of the one-dimensional wire with respect to the position of the barrier in the drag wire. When we additionally form a potential barrier in the drive wire, the direction of the drag current is determined by the relative position of the two barriers. We interpret this behavior in terms of electron excitations by phonon-mediated interactions between the two wires in presence of the electron scattering inside the drive wire. △ Less

Submitted 25 October, 2021; v1 submitted 19 July, 2021; originally announced July 2021.

Comments: Main paper: 10 pages, 4 figures, Supplemental material: 6 pages, 3 figures

Journal ref: J. Phys. Soc. Jpn. 90, 113707 (2021)

Drag of Two Cylindrical Intruders in a Two-Dimensional Granular Environment

Authors: Takumi Kubota, Haruto Ishikawa, Satoshi Takada

Abstract: The drag of two cylindrical intruders in a two-dimensional granular environment is numerically studied by the discrete element method. We find the yield force, below which the intruders cannot move because of interactions with the surrounding particles. Above the yield force, on the other hand, the intruders can move at a constant speed. We investigate the relationship between the drag force and t… ▽ More The drag of two cylindrical intruders in a two-dimensional granular environment is numerically studied by the discrete element method. We find the yield force, below which the intruders cannot move because of interactions with the surrounding particles. Above the yield force, on the other hand, the intruders can move at a constant speed. We investigate the relationship between the drag force and the steady speed of the intruders, where the speed becomes higher as the distance between the intruders decreases. We confirm that the origin of the yield is the Coulombic friction between the particles and the bottom plate by changing the value of the friction coefficient. We also find that the yield force is almost proportional to the friction coefficient, which means that the number of particles determining the yield force is almost constant. On the other hand, the two-dimensional elasticity is applicable to determine the stress fields around the intruders. We confirm that fields asymmetric with respect to the drag direction are reproduced by using the information of the stresses on the surfaces of the intruders by introducing bipolar coordinates. △ Less

Submitted 24 March, 2022; v1 submitted 23 May, 2021; originally announced May 2021.

Comments: 9 pages, 10 figures, 1 table

Impact of Softness of Particles on Rheology of Dilute Granular Gases

Authors: Haruto Ishikawa, Satoshi Takada

Abstract: We numerically and theoretically investigate how the softness of particles affects the rheology of sheared dilute granular gases. We find that the kinetic theory predicts the deviation of the flow curve from the Bagnold scaling, and it works well below a certain shear rate when we compare with the simulation results. It is also found that there is no theoretical solution above this shear rate, whi… ▽ More We numerically and theoretically investigate how the softness of particles affects the rheology of sheared dilute granular gases. We find that the kinetic theory predicts the deviation of the flow curve from the Bagnold scaling, and it works well below a certain shear rate when we compare with the simulation results. It is also found that there is no theoretical solution above this shear rate, which is because the energy loss due to inelastic collisions cannot be balanced with the energy injection by the shear. △ Less

Submitted 20 May, 2021; originally announced May 2021.

Comments: 5 pages, 4 figures, 1 table

Journal ref: J. Phys. Soc. Jpn. 90, 064801 (2021)

Mpemba effect in inertial suspensions

Authors: Satoshi Takada, Hisao Hayakawa, Andrés Santos

Abstract: The Mpemba effect (a counterintuitive thermal relaxation process where an initially hotter system may cool down to the steady state sooner than an initially colder system) is studied in terms of a model of inertial suspensions under shear. The relaxation to a common steady state of a suspension initially prepared in a quasi-equilibrium state is compared with that of a suspension initially prepared… ▽ More The Mpemba effect (a counterintuitive thermal relaxation process where an initially hotter system may cool down to the steady state sooner than an initially colder system) is studied in terms of a model of inertial suspensions under shear. The relaxation to a common steady state of a suspension initially prepared in a quasi-equilibrium state is compared with that of a suspension initially prepared in a nonequilibrium sheared state. Two classes of Mpemba effect are identified, the normal and the anomalous one. The former is generic, in the sense that the kinetic temperature starting from a cold nonequilibrium sheared state is overtaken by the one starting from a hot quasi-equilibrium state, due to the absence of initial viscous heating in the latter, resulting in a faster initial cooling. The anomalous Mpemba effect is opposite to the normal one since, despite the initial slower cooling of the nonequilibrium sheared state, it can eventually overtake an initially colder quasi-equilibrium state. The theoretical results based on kinetic theory agree with those obtained from event-driven simulations for inelastic hard spheres. It is also confirmed the existence of the inverse Mpemba effect, which is a peculiar heating process, in these suspensions. More particularly, we find the existence of a mixed process in which both heating and cooling can be observed during relaxation. △ Less

Submitted 10 February, 2021; v1 submitted 2 November, 2020; originally announced November 2020.

Comments: 28 pages, 20 figures

Journal ref: Phys. Rev. E 103, 032901 (2021)

Two-Step Discontinuous Shear Thickening of Dilute Inertial Suspensions Having Soft-Core Potential

Authors: Shuichi Sugimoto, Satoshi Takada

Abstract: Kinetic theory for dilute inertial suspension having soft-core potential is theoretically investigated. From the analysis of the scattering process, the expression of the scattering angle is analytically obtained. We derive the flow curve between the viscosity and the shear rate, which shows two-step discontinuous shear thickening when we change the softness of the particles. The molecular dynamic… ▽ More Kinetic theory for dilute inertial suspension having soft-core potential is theoretically investigated. From the analysis of the scattering process, the expression of the scattering angle is analytically obtained. We derive the flow curve between the viscosity and the shear rate, which shows two-step discontinuous shear thickening when we change the softness of the particles. The molecular dynamics simulation shows that our theoretical results are consistent with the numerical ones. △ Less

Submitted 19 October, 2020; v1 submitted 15 July, 2020; originally announced July 2020.

Comments: 11 pages, 7 figures. Some typos are modified, and an addendum is added

Journal ref: J. Phys. Soc. Jpn. 89, 084803 (2020)

Enskog kinetic theory of rheology for a moderately dense inertial suspension

Authors: Satoshi Takada, Hisao Hayakawa, Andrés Santos, Vicente Garzó

Abstract: The Enskog kinetic theory for moderately dense inertial suspensions under simple shear flow is considered as a model to analyze the rheological properties of the system. The influence of the background fluid on suspended particles is modeled via a viscous drag force plus a Langevin-like term defined in terms of the background temperature. In a previous paper [Hayakawa et al., Phys. Rev. E 96, 0429… ▽ More The Enskog kinetic theory for moderately dense inertial suspensions under simple shear flow is considered as a model to analyze the rheological properties of the system. The influence of the background fluid on suspended particles is modeled via a viscous drag force plus a Langevin-like term defined in terms of the background temperature. In a previous paper [Hayakawa et al., Phys. Rev. E 96, 042903 (2017)], Grad's moment method with the aid of a linear shear-rate expansion was employed to obtain a theory which gave good agreement with the results of event-driven Langevin simulations of hard spheres for low densities and/or small shear rates. Nevertheless, the previous approach had a limitation of applicability to the high shear-rate and high density regime. Thus, in the present paper, we extend the previous work and develop Grad's theory including higher order terms in the shear rate. This improves significantly the theoretical predictions, a quantitative agreement between theory and simulation being found in the high-density region (volume fractions smaller than or equal to $0.4$). △ Less

Submitted 1 August, 2020; v1 submitted 12 May, 2020; originally announced May 2020.

Comments: 27 pages, 9 figures. arXiv admin note: text overlap with arXiv:1707.09694

Journal ref: Phys. Rev. E 102, 022907 (2020)

Remotely pumped GHz antibunched emission from single exciton centers in GaAs

Authors: M. Yuan, K. Biermann, S. Takada, C. Bäuerle, P. V. Santos

Abstract: Quantum communication networks require on-chip transfer and manipulation of single particles as well as their interconversion to single photons for long-range information exchange. Flying excitons propelled by GHz surface acoustic waves (SAWs) are outstanding messengers to fulfill these requirements. Here, we demonstrate the acoustic manipulation of single exciton centers consisting of individual… ▽ More Quantum communication networks require on-chip transfer and manipulation of single particles as well as their interconversion to single photons for long-range information exchange. Flying excitons propelled by GHz surface acoustic waves (SAWs) are outstanding messengers to fulfill these requirements. Here, we demonstrate the acoustic manipulation of single exciton centers consisting of individual excitons bound to shallow impurities centers embedded in a semiconductor quantum well. Time-resolved photoluminescence studies show that the emission intensity and energy from these centers oscillate at the SAW frequency of 3.5 GHz. Furthermore, these centers can be remotely pumped via acoustic transport of flying excitons along a quantum well channel over several microns. Time correlation studies reveal that the centers emit anti-bunched light, thus acting as single-photon sources operating at GHz frequencies. Our results pave the way for the exciton-based on-demand manipulation and on-chip transfer of single excitons at microwave frequencies with a natural photonic interface. △ Less

Submitted 9 March, 2021; v1 submitted 11 May, 2020; originally announced May 2020.

Comments: Main text: 20 pages, 5 figures. Supporting Information: 5 pages, 4 figures

Journal ref: ACS Photonics 8 (2021) 758-764

Coherent beam splitting of flying electrons driven by a surface acoustic wave

Authors: R. Ito, S. Takada, A. Ludwig, A. D. Wieck, S. Tarucha, M. Yamamoto

Abstract: We develop a coherent beam splitter for single electrons driven through two tunnel-coupled quantum wires by surface acoustic waves (SAWs). The output current through each wire oscillates with gate voltages to tune the tunnel-coupling and potential difference between the wires. This oscillation is assigned to coherent electron tunneling motion that can be used to encode a flying qubit and is well r… ▽ More We develop a coherent beam splitter for single electrons driven through two tunnel-coupled quantum wires by surface acoustic waves (SAWs). The output current through each wire oscillates with gate voltages to tune the tunnel-coupling and potential difference between the wires. This oscillation is assigned to coherent electron tunneling motion that can be used to encode a flying qubit and is well reproduced by numerical calculations of time evolution of the SAW-driven single electrons. The oscillation visibility is currently limited to about 3%, but robust against decoherence, indicating that the SAW-electron can serve as a novel platform for a solid-state flying qubit. △ Less

Submitted 24 April, 2020; originally announced April 2020.

Comments: 5+3 pages, 4+2 figures

Journal ref: Phys. Rev. Lett. 126, 070501 (2021)

Ground state modulations in the ${\mathbb C}P^{N-1}$ model

Authors: Antonino Flachi, Guglielmo Fucci, Muneto Nitta, Satoshi Takada, Ryosuke Yoshii

Abstract: In this work we examine a system consisting of a confined one-dimensional arrangement of atoms that we describe by using the 2-dimensional ${\mathbb C}P^{N-1}$ model, restricted to an interval and at finite temperature. We develop a method to obtain the bulk and boundary parts of the one-loop effective action as a function of the effective mass of the fluctuations. The formalism has the advantage… ▽ More In this work we examine a system consisting of a confined one-dimensional arrangement of atoms that we describe by using the 2-dimensional ${\mathbb C}P^{N-1}$ model, restricted to an interval and at finite temperature. We develop a method to obtain the bulk and boundary parts of the one-loop effective action as a function of the effective mass of the fluctuations. The formalism has the advantage of allowing for a systematic analysis of a large class of boundary conditions and to model the (adiabatic) response of the ground state to changes in the boundary conditions. In the case of periodic boundary conditions, we find that inhomogeneous phases are disfavored for intervals of large size. Away from periodic boundary conditions, our numerical results show that the ground state has a generic crystal-like structure that can be modulated by variations of the boundary conditions. The results presented here could be relevant for experimental implementations of nonlinear sigma models and could be tested by lattice numerical simulations. △ Less

Submitted 18 October, 2019; v1 submitted 28 June, 2019; originally announced July 2019.

Comments: 7 pages; 1 figure; revised version

Journal ref: Phys. Rev. D 100, 085006 (2019)

Particle flows around an intruder

Authors: Satoshi Takada, Hisao Hayakawa

Abstract: Particle flows injected as beams and scattered by an intruder are numerically studied. We find a crossover of the drag force from Epstein's law to Newton's law, depending on the ratio of the speed to the thermal speed. These laws can be reproduced by a simple analysis of a collision model between the intruder and particle flows. The crossover from Epstein's law to Stokes' law is also found for the… ▽ More Particle flows injected as beams and scattered by an intruder are numerically studied. We find a crossover of the drag force from Epstein's law to Newton's law, depending on the ratio of the speed to the thermal speed. These laws can be reproduced by a simple analysis of a collision model between the intruder and particle flows. The crossover from Epstein's law to Stokes' law is also found for the low-speed regime as the time evolution of the drag force caused by beam particles. We also show the existence of turbulent-like behavior of the particle flows behind the intruder with the aid of the second invariant of the velocity gradient tensor and the relative mean square displacement for the high-speed regime and a large intruder. △ Less

Submitted 11 August, 2020; v1 submitted 28 April, 2019; originally announced April 2019.

Comments: 10 pages, 13 figures

Journal ref: Phys. Rev. Research 2, 033468 (2020)

Sound-driven single-electron transfer in a circuit of coupled quantum rails

Authors: Shintaro Takada, Hermann Edlbauer, Hugo V. Lepage, Junliang Wang, Pierre-André Mortemousque, Giorgos Georgiou, Crispin H. W. Barnes, Chris J. B. Ford, Mingyun Yuan, Paulo V. Santos, Xavier Waintal, Arne Ludwig, Andreas D. Wieck, Matias Urdampilleta, Tristan Meunier, Christopher Bäuerle

Abstract: Surface acoustic waves (SAWs) strongly modulate the shallow electric potential in piezoelectric materials. In semiconductor heterostructures such as GaAs/AlGaAs, SAWs can thus be employed to transfer individual electrons between distant quantum dots. This transfer mechanism makes SAW technologies a promising candidate to convey quantum information through a circuit of quantum logic gates. Here we… ▽ More Surface acoustic waves (SAWs) strongly modulate the shallow electric potential in piezoelectric materials. In semiconductor heterostructures such as GaAs/AlGaAs, SAWs can thus be employed to transfer individual electrons between distant quantum dots. This transfer mechanism makes SAW technologies a promising candidate to convey quantum information through a circuit of quantum logic gates. Here we present two essential building blocks of such a SAW-driven quantum circuit. First, we implement a directional coupler allowing to partition a flying electron arbitrarily into two paths of transportation. Second, we demonstrate a triggered single-electron source enabling synchronisation of the SAW-driven sending process. Exceeding a single-shot transfer efficiency of 99 %, we show that a SAW-driven integrated circuit is feasible with single electrons on a large scale. Our results pave the way to perform quantum logic operations with flying electron qubits. △ Less

Submitted 23 September, 2019; v1 submitted 2 March, 2019; originally announced March 2019.

Comments: Accepted for Publication in Nature Communications

Journal ref: Nature Communications 10, 4557 (2019)

Drag acting on an intruder in a three-dimensional granular environment

Authors: Satoshi Takada, Hisao Hayakawa

Abstract: The drag acting on an intruder in a three-dimensional frictionless dry granular environment is numerically studied. It is found the followings: (i) There is no yield force for the motion of the intruder without the gravity. (ii) The drag is proportional to the cross section of the moving intruder. (iii) If the intruder is larger than surrounding grains, the drag is proportional to the moving speed… ▽ More The drag acting on an intruder in a three-dimensional frictionless dry granular environment is numerically studied. It is found the followings: (i) There is no yield force for the motion of the intruder without the gravity. (ii) The drag is proportional to the cross section of the moving intruder. (iii) If the intruder is larger than surrounding grains, the drag is proportional to the moving speed $V$ of the intruder for dense systems, but it exhibits a crossover from quadratic to linear dependences of the moving speed when the volume fraction of the surrounding grains is much lower than the jamming point. (iv) There is a plateau regime where the drag is almost independent of $V$ if the size of the intruder is identical to those of the environmental grains and the volume fraction is near the jamming point. △ Less

Submitted 1 November, 2019; v1 submitted 8 January, 2019; originally announced January 2019.

Comments: 6 pages, 7 figures, Granular Matter in press

Journal ref: Granul. Matter 22, 6 (2020)

Coherent control of single electrons: a review of current progress

Authors: Christopher Bauerle, D. Christian Glattli, Tristan Meunier, Fabien Portier, Patrice Roche, Preden Roulleau, Shintaro Takada, Xavier Waintal

Abstract: In this report we review the present state of the art of the control of propagating quantum states at the single-electron level and its potential application to quantum information processing. We give an overview of the different approaches which have been developed over the last ten years in order to gain full control over a propagating single electron in a solid state system. After a brief intro… ▽ More In this report we review the present state of the art of the control of propagating quantum states at the single-electron level and its potential application to quantum information processing. We give an overview of the different approaches which have been developed over the last ten years in order to gain full control over a propagating single electron in a solid state system. After a brief introduction of the basic concepts, we present experiments on flying qubit circuits for ensemble of electrons measured in the low frequency (DC) limit. We then present the basic ingredients necessary to realise such experiments at the single-electron level. This includes a review of the various single electron sources which are compatible with integrated single electron circuits. This is followed by a review of recent key experiments on electron quantum optics with single electrons. Finally we will present recent developments about the new physics that emerges using ultrashort voltage pulses. We conclude our review with an outlook and future challenges in the field. △ Less

Submitted 1 February, 2018; v1 submitted 23 January, 2018; originally announced January 2018.

Comments: 35 pages, 24 figures, This is an author-created, un-copyedited version of an article accepted for publication in Rep. Prog. Phys. (references added)

Journal ref: Rep. Prog. Phys. 81 056503 (pp33) (2018)

Scaling law of the drag force in dense granular media

Authors: Sonu Kumar, K. Anki Reddy, Satoshi Takada, Hisao Hayakawa

Abstract: Making use of the system of pulling a spherical intruder in static three-dimensional granular media, we numerically study the scaling law for the drag force $F_{\rm drag}$ acting on the moving intruder under the influence of the gravity. Suppose if the intruder of diameter $D$ immersed in a granular medium consisting of grains of average diameter $d$ is located at a depth $h$ and moves with a spee… ▽ More Making use of the system of pulling a spherical intruder in static three-dimensional granular media, we numerically study the scaling law for the drag force $F_{\rm drag}$ acting on the moving intruder under the influence of the gravity. Suppose if the intruder of diameter $D$ immersed in a granular medium consisting of grains of average diameter $d$ is located at a depth $h$ and moves with a speed $V$, we find that $F_{\rm drag}$ can be scaled as $(D+d)^{φ_μ} h^{α_μ}$ with two exponents $φ_μ$ and $α_μ$, which depend on the friction coefficient $μ$ and satisfy an approximate sum rule $φ_μ+α_μ\approx 3$. This scaling law is valid for the arbitrary Froude number (defined by $\mathrm{Fr}={2 V}\sqrt{{2D}/{g}}\big/(D+d)$), if $h$ is sufficiently deep. We also identify the existence of three regimes (quasistatic, linear, and quadratic) at least for frictional grains in the velocity dependence of drag force. The crossovers take place at $\mathrm{Fr}\approx 1$ between the quasistatic to the linear regimes and at $\mathrm{Fr}\approx 5$ between the linear to the quadratic regimes. We also observe that Froude numbers at which these crossovers between the regimes happen are independent of the depth $h$ and the diameter of the intruder $D$. We also report the numerical results on the average coordination number of the intruder and average contact angle as functions of intruder velocity. △ Less

Submitted 12 May, 2020; v1 submitted 25 December, 2017; originally announced December 2017.

Comments: 15 pages, 20 figures