Showing 1–46 of 46 results for author: Ricco, S

Engineering Tunable Synthetic Su-Schrieffer-Heeger Chains in Liquid Crystal Microcavities

Authors: Joanna Mędrzycka, Luciano S. Ricco, Piotr Kapuściński, Marcin Muszyński, Przemysław Morawiak, Rafał Mazur, Rafał Węgłowski, Eva Oton, Przemysław Kula, Wiktor Piecek, Jacek Szczytko

Abstract: Optical microcavities have emerged as a powerful platform for emulating topological phases challenging to realize in conventional materials, offering precise control over dispersion, light confinement, and interactions. Among them, liquid crystal microcavities (LCMCs) offer exceptional tunability at room temperature, enabling voltage-controlled polarisation splitting, photonic spin-orbit coupling,… ▽ More Optical microcavities have emerged as a powerful platform for emulating topological phases challenging to realize in conventional materials, offering precise control over dispersion, light confinement, and interactions. Among them, liquid crystal microcavities (LCMCs) offer exceptional tunability at room temperature, enabling voltage-controlled polarisation splitting, photonic spin-orbit coupling, and photonic potentials generated by self-assembled textures, such as cholesteric torons and uniform lying helix (ULH). Here, we design a LCMC hosting a dimerized ULH texture and show that the corresponding photonic potential describes two coupled Su-Schrieffer-Heeger chains with orthogonal linear polarisations, acting as an effective pseudospin degree of freedom. The applied voltage tunes the interchain coupling, enabling polarisation-dependent interactions. These results establish LCMCs as a versatile platform for tunable synthetic topological Hamiltonians. △ Less

Submitted 19 May, 2026; originally announced May 2026.

Revisiting the Poor Man's Majoranas: The Spin-Exchange Induced Spillover Effect

Authors: J. E. Sanches, T. M. Sobreira, L. S. Ricco, M. S. Figueira, A. C. Seridonio

Abstract: We give a review on Poor Man's Majorana (PMM) modes, which are theoretically established in the minimal Kitaev chain implementation consisting of two grounded, spinless quantum dots (QDs) operating at the sweet spot condition, where electron cotunneling and crossed Andreev reflection amplitudes achieve precise balance. Particularly, we systematically review, within the Green's functions theoretica… ▽ More We give a review on Poor Man's Majorana (PMM) modes, which are theoretically established in the minimal Kitaev chain implementation consisting of two grounded, spinless quantum dots (QDs) operating at the sweet spot condition, where electron cotunneling and crossed Andreev reflection amplitudes achieve precise balance. Particularly, we systematically review, within the Green's functions theoretical framework, the PMM hybridization dynamics under spin-exchange perturbations proposed by some of us in J. Phys.: Condens. Matter 37, 205601 (2025), which demonstrates a characteristic spatial delocalization when subjected to an exchange coupling $J$ mediated by a quantum spin $S$. This spin-exchange induced PMM spillover effect provides a spectroscopic protocol for determining the quantum statistics of $S$ through the emergent multi-level structure in the proximal QD's density of states. Our principal theoretical result establishes that the exchange interaction generates $2S+2$ ($2S+1$) satellite states symmetrically distributed about the zero-bias anomaly, serving as a definitive signature of bosonic (fermionic) spin statistics. As novelty, we demonstrate that multi-terminal environmental coupling induces significant suppression of the spin-exchange spillover mechanism. Under constrained variations of $J$, this effectively localizes the perturbed PMM within its host QD, preventing spatial hybridization with adjacent site. The absence of topological protection in this minimal Kitaev realization is strategically leveraged to: (i) Develop a novel spectroscopic technique for quantum spin characterization through PMM hybridization signatures; (ii) Propose the "environmentally induced protection", an engineered dissipative spectral stabilization for PMMs against exchange fluctuations in multi-terminal architectures. △ Less

Submitted 10 January, 2026; v1 submitted 5 September, 2025; originally announced September 2025.

Journal ref: J. Phys.: Condens. Matter 38 023001 (2026)

Phase transitions induced by resonant light: a phenomenological approach

Authors: A. Kudlis, L. S. Ricco, H. Sigurðsson, I. A. Shelykh

Abstract: We present a phenomenological framework to describe a subclass of light-induced phase transitions (LIPTs) in condensed matter systems, specifically those mediated by the resonant generation of excitons. Our approach extends the classical Landau theory by introducing dynamic coupling between the system's order parameter and complex excitonic fields, along with Langevin-type forces that drive the sy… ▽ More We present a phenomenological framework to describe a subclass of light-induced phase transitions (LIPTs) in condensed matter systems, specifically those mediated by the resonant generation of excitons. Our approach extends the classical Landau theory by introducing dynamic coupling between the system's order parameter and complex excitonic fields, along with Langevin-type forces that drive the system toward states of minimal free energy. The model is applied in the context of all-optical resonant magnetization switching in two-dimensional magnetic materials, particularly reproducing the experimental findings for reverse magnetization by all-optical means for a monolayer CrI$_3$. Our phenomenological model can be applied to other systems characterized by an order parameter and excitonic fields created through resonant light, offering versatility and potential to guide future experimental and theoretical studies in LIPT phenomena. △ Less

Submitted 10 January, 2026; v1 submitted 6 June, 2025; originally announced June 2025.

Electrically reconfigurable extended lasing state in an organic liquid-crystal microcavity

Authors: Dmitriy Dovzhenko, Luciano Siliano Ricco, Krzysztof Sawicki, Marcin Muszyński, Pavel Kokhanchik, Piotr Kapuściński, Przemysław Morawiak, Wiktor Piecek, Piotr Nyga, Przemysław Kula, Dmitry Solnyshkov, Guillaume Malpuech, Helgi Sigurðsson, Jacek Szczytko, Simone De Liberato

Abstract: Small-footprint, low-power arrays of coupled coherent emitters with the capability of near- and far-field engineering and coherence control are highly sought after to meet modern nanophotonics evolving needs. Between existing solutions based on vertical-cavity surface-emitting lasers, phase masks in bulk traditional cavity-based systems, and lattices of exciton-polariton condensates, only the stro… ▽ More Small-footprint, low-power arrays of coupled coherent emitters with the capability of near- and far-field engineering and coherence control are highly sought after to meet modern nanophotonics evolving needs. Between existing solutions based on vertical-cavity surface-emitting lasers, phase masks in bulk traditional cavity-based systems, and lattices of exciton-polariton condensates, only the strongly light-matter coupled systems were shown to be capable of controlled on-chip interaction between the individual coherent states while often operating at cryogenic temperatures. Here we demonstrate electrically controlled in-plane interaction between optically reconfigurable spatially separated lasing states, operating at room temperature in the weak light-matter coupling regime. We show spatially extended coherent lasing state or "supermode" with wide-range micro-scale control of near-field, far-field and on-chip phase-locking tuning functionality. An extended lasing state appears due to near-field transverse coupling between distinct spatially pumped lasing states in the plane of an organic liquid crystal-filled microcavity. We realize electrical control over the interaction strength between lasing states and corresponding mutual coherence going beyond nearest neighbours through electrical tuning of the microcavity optical modes with external voltage, and a spin-selective directional coupling regime by using a photonic analogue of the Rashba-Dresselhaus spin-orbit interaction. △ Less

Submitted 24 April, 2026; v1 submitted 5 June, 2025; originally announced June 2025.

Comments: 32 pages, 14 figures

Spin-Exchange Induced Spillover on Poor Man's Majoranas in Minimal Kitaev Chains

Authors: J. E. Sanches, L. T. Lustosa, L. S. Ricco, H. Sigurðsson, M. de Souza, M. S. Figueira, E. Marinho Jr., A. C. Seridonio

Abstract: The "Poor Man's Majoranas" (PMMs) [Phys. Rev. B 86, 134528 (2012)] devoid of topological protection can "spill over" from one edge into another of the minimal Kitaev chain when perturbed electrostatically. As aftermath, this leads to a delocalized Majorana fermion (MF) at both the edges. Additionally, according to recent differential conductance measurements in a pair of superconducting and spinle… ▽ More The "Poor Man's Majoranas" (PMMs) [Phys. Rev. B 86, 134528 (2012)] devoid of topological protection can "spill over" from one edge into another of the minimal Kitaev chain when perturbed electrostatically. As aftermath, this leads to a delocalized Majorana fermion (MF) at both the edges. Additionally, according to recent differential conductance measurements in a pair of superconducting and spinless quantum dots (QDs), such a PMM picture was brought to reality [Nature 614, 445 (2023) and Nature 630, 329 (2024)]. Based on this scenario, we propose the spillover of the PMM when its QD is exchange coupled to a quantum spin $S$. We show that if this QD is perturbed by the exchange coupling $J$, solely the half $2S+1$ $(2S+2)$ of the fine structure stays explicit for a fermionic (bosonic) $S.$ Concurrently, the other half squeezes itself as the delocalized MF zero-mode. Particularly, turning-off the superconductivity the multiplicity $2S+1$ holds regardless the spin statistics. Meanwhile, the PMM spillover induced by $J$ becomes a statistics dependent effect. Hence, our findings contribute to the comprehension of spin-phenomena interplay with superconductivity in minimal Kitaev chains, offering insights for future quantum computing devices hosting PMMs. △ Less

Submitted 28 April, 2025; originally announced April 2025.

Journal ref: Journal of Physics: Condensed Matter, Volume 37, Number 20, 205601 (2025)

Fermi surface and pseudogap in highly doped Sr$_{2}$IrO$_{4}$

Authors: Y. Alexanian, A. de la Torre, S. McKweon Walker, M. Straub, G. Gatti, A. Hunter, S. Mandloi, E. Cappelli, S. Riccò, F. Y. Bruno, M. Radovic, N. C. Plumb, M. Shi, J. Osiecki, C. Polley, T. K. Kim, P. Dudin, M. Hoesch, R. S. Perry, A. Tamai, F. Baumberger

Abstract: The fate of the Fermi surface in bulk electron-doped Sr$_{2}$IrO$_{4}$ remains elusive, as does the origin and extension of its pseudogap phase. Here, we use high-resolution angle-resolved photoelectron spectroscopy (ARPES) to investigate the electronic structure of Sr$_{2-x}$La$_{x}$IrO$_{4}$ up to $x=0.2$, a factor of two higher than in previous work. We find that the antinodal pseudogap persist… ▽ More The fate of the Fermi surface in bulk electron-doped Sr$_{2}$IrO$_{4}$ remains elusive, as does the origin and extension of its pseudogap phase. Here, we use high-resolution angle-resolved photoelectron spectroscopy (ARPES) to investigate the electronic structure of Sr$_{2-x}$La$_{x}$IrO$_{4}$ up to $x=0.2$, a factor of two higher than in previous work. We find that the antinodal pseudogap persists up to the highest doping level, and thus beyond the sharp increase in Hall carrier density to $\simeq 1+x$ recently observed above $x^{*}\simeq 0.16$ [Y.-T. Hsu et al., Nature Physics 20, 1593 (2024)]. This suggests that doped iridates host a unique phase of matter in which a large Hall density coexists with an anisotropic pseudogap, breaking up the Fermi surface into disconnected arcs. The temperature boundary of the pseudogap is $T^{*}\simeq 200$ K for $x=0.2$, comparable to cuprates and to the energy scale of short range antiferromagnetic correlations in cuprates and iridates. △ Less

Submitted 4 September, 2025; v1 submitted 27 November, 2024; originally announced November 2024.

Comments: 9 pages, 4 figures. Supplementary Information: 3 pages, 3 figures

Journal ref: npj Quantum Materials 10, 100 (2025)

Cellular Griffiths-like phase

Authors: Lucas Squillante, Isys F. Mello, Luciano S. Ricco, Marcos F. Minicucci, Aniekan Magnus Ukpong, Antonio C. Seridonio, Roberto E. Lagos-Monaco, Mariano de Souza

Abstract: Protein compartmentalization in the frame of a liquid-liquid phase separation is a key mechanism to optimize spatiotemporal control of biological systems. Such a compartmentalization process reduces the intrinsic noise in protein concentration due to stochasticity in gene expression. Employing Flory-Huggins solution theory, Avramov/Casalini's model, and the Grüneisen parameter, we unprecedentedly… ▽ More Protein compartmentalization in the frame of a liquid-liquid phase separation is a key mechanism to optimize spatiotemporal control of biological systems. Such a compartmentalization process reduces the intrinsic noise in protein concentration due to stochasticity in gene expression. Employing Flory-Huggins solution theory, Avramov/Casalini's model, and the Grüneisen parameter, we unprecedentedly propose a cellular Griffiths-like phase (CGLP), which can impact its functionality and self-organization. The here-proposed CGLP is key ranging from the understanding of primary organisms' evolution to the treatment of diseases. Our findings pave the way for an alternative Biophysics approach to investigate coacervation processes. △ Less

Submitted 25 September, 2024; originally announced September 2024.

Comments: 13 pages, 2 figures, suppl. material upon request

Journal ref: Heliyon 10, e34622 (2024)

Squeezed state protection of fine structure in "Poor Man's Majorana" via quantum spin coupling

Authors: J. E. Sanches, L. T. Lustosa, L. S. Ricco, H. Sigurðsson, M. de Souza, M. S. Figueira, E. Marinho Jr., A. C. Seridonio

Abstract: The "Poor Man's Majorana" [Phys. Rev. B 86, 134528 (2012)] devoid of topological protection has been theoretically predicted to rely on the minimal Kitaev chain. Afterward, a pair of superconducting and spinless quantum dots turned the proposal practicable and differential conductance pinpointed consistent fingerprints with such a scenario [Nature 614, 445 (2023) and Nature 630, 329 (2024)]. In th… ▽ More The "Poor Man's Majorana" [Phys. Rev. B 86, 134528 (2012)] devoid of topological protection has been theoretically predicted to rely on the minimal Kitaev chain. Afterward, a pair of superconducting and spinless quantum dots turned the proposal practicable and differential conductance pinpointed consistent fingerprints with such a scenario [Nature 614, 445 (2023) and Nature 630, 329 (2024)]. In this work, we propose a model wherein the "Poor Man's Majorana" presents protection when one of the dots is exchange coupled to a quantum spin. If this quantum dot is perturbed by tuning the exchange coupling, the well-known spill over-like behavior of this Majorana surprisingly remains unchanged, and solely half of the fine structure is unexpectedly viewed. As a matter of fact, the "Poor Man's Majorana" zero mode consists in squeezing of the other half at zero frequency, which imposes its pinning there and prevents the mixing of the mode with the explicit fine structure. We claim that if the supposed unavoidable split of the zero mode by the fine structure is unexpectedly absent, then the "Poor Man's Majorana" can be considered robust against the quantum spin. In this way, it becomes protected and the lack of topological protection paradigm of the "Poor Man's Majorana" has been revisited, pushing this seemingly well-established issue into a new direction. △ Less

Submitted 27 August, 2024; originally announced August 2024.

Spin-Polarized Majorana Zero Modes in Proximitized Superconducting Penta-Silicene Nanoribbons

Authors: R. C. Bento Ribeiro, J. H. Correa, L. S. Ricco, I. A. Shelykh, M. A. Continentino, A. C. Seridonio, M. Minissale, G. L. Lay, M. S. Figueira

Abstract: We theoretically investigate the possibility of obtaining Majorana zero modes (MZMs) in penta-silicene nanoribbons (p-SiNRs) with induced \textit{p}-wave superconductivity. The model explicitly considers an external magnetic field perpendicularly applied to the nanoribbon plane, as well as an extrinsic Rashba spin-orbit coupling (RSOC), in addition to the first nearest neighbor hopping term and \t… ▽ More We theoretically investigate the possibility of obtaining Majorana zero modes (MZMs) in penta-silicene nanoribbons (p-SiNRs) with induced \textit{p}-wave superconductivity. The model explicitly considers an external magnetic field perpendicularly applied to the nanoribbon plane, as well as an extrinsic Rashba spin-orbit coupling (RSOC), in addition to the first nearest neighbor hopping term and \textit{p}-wave superconducting pairing. By analyzing the dispersion relation profiles, we observe the successive closing and reopening of the induced superconducting gap with a single spin component, indicating a spin-polarized topological phase transition (TPT). Correspondingly, the plots of the energy spectrum versus the chemical potential reveal the existence of zero-energy states with a preferential spin orientation characterized by nonoverlapping wave functions localized at opposite ends of the superconducting p-SiNRs. These findings strongly suggest the emergence of topologically protected, spin-polarized MZMs at the ends of the p-SiNRs with induced \textit{p}-wave superconducting pairing, which can be realized by proximitizing the nanoribbon with an \textit{s}-wave superconductor, such as lead. The proposal paves the way for silicene-based Majorana devices hosting multiple MZMs with a well-defined spin orientation, with possible applications in fault-tolerant quantum computing platforms and Majorana spintronics. △ Less

Submitted 6 July, 2023; originally announced July 2023.

Comments: 12 pages, 9 figures

Grüneisen parameter as an entanglement compass and the breakdown of the Hellmann-Feynman theorem

Authors: Lucas Squillante, Luciano S. Ricco, Aniekan Magnus Ukpong, Roberto E. Lagos-Monaco, Antonio C. Seridonio, Mariano de Souza

Abstract: The Grüneisen ratio $Γ$, i.e., the singular part of the ratio of thermal expansion to the specific heat, has been broadly employed to explore both finite-$T$ and quantum critical points (QCPs). For a genuine quantum phase transition (QPT), thermal fluctuations are absent and thus the thermodynamic $Γ$ cannot be employed. We propose a quantum analogue to $Γ$ that computes entanglement as a function… ▽ More The Grüneisen ratio $Γ$, i.e., the singular part of the ratio of thermal expansion to the specific heat, has been broadly employed to explore both finite-$T$ and quantum critical points (QCPs). For a genuine quantum phase transition (QPT), thermal fluctuations are absent and thus the thermodynamic $Γ$ cannot be employed. We propose a quantum analogue to $Γ$ that computes entanglement as a function of a tuning parameter $λ$ and show that QPTs take place only for systems in which the ground-state energy depends on $λ$ non-linearly. Furthermore, we demonstrate the breakdown of the Hellmann-Feynman theorem in the thermodynamic limit at any QCP. We showcase our approach using the quantum 1D Ising model with transverse field and Kane's quantum computer. The slowing down of the dynamics and thus the "creation of mass" close to any QCP/QPT is also discussed. △ Less

Submitted 25 September, 2024; v1 submitted 1 June, 2023; originally announced June 2023.

Comments: 5 pages, 3 figures, comments are wellcome!

Journal ref: Physical Review B 108, L140403 (2023)

Fractionalization of Majorana-Ising-type quasiparticles

Authors: J. E. Sanches, L. T. Lustosa, L. S. Ricco, I. A. Shelykh, M. de Souza, M. S. Figueira, A. C. Seridonio

Abstract: We theoretically investigate the spectral properties of a quantum impurity (QI) hosting the here proposed {Majorana-Ising-type quasiparticle (MIQ) excitation}. It arises from the coupling between a finite topological superconductor (TSC) based on a chain of magnetic adatoms-superconducting hybrid system and an integer large spin $S$ flanking the QI. Noteworthy, the spin $S$ couples to the QI via t… ▽ More We theoretically investigate the spectral properties of a quantum impurity (QI) hosting the here proposed {Majorana-Ising-type quasiparticle (MIQ) excitation}. It arises from the coupling between a finite topological superconductor (TSC) based on a chain of magnetic adatoms-superconducting hybrid system and an integer large spin $S$ flanking the QI. Noteworthy, the spin $S$ couples to the QI via the Ising-type exchange interaction. As the Majorana zero-modes (MZMs) at the edges of the TSC chain are overlapped, we counterintuitively find a regime wherein the Ising term modulates the localization of a fractionalized and resonant MZM at the QI site. Interestingly enough, the fermionic nature of this state is revealed as purely of electron tunneling-type and most astonishingly, it has the Andreev conductance completely null in its birth. Therefore, we find that a resonant edge state appears as a zero-mode and discuss it in terms of a poor man's Majorana[Nature 614, 445 (2023)]. △ Less

Submitted 11 December, 2023; v1 submitted 9 January, 2023; originally announced January 2023.

Reshaping the Jaynes-Cummings ladder with Majorana bound states

Authors: L. S. Ricco, V. K. Kozin, A. C. Seridonio, I. A. Shelykh

Abstract: We study the optical properties of a hybrid device composed by a quantum dot (QD) resonantly coupled to a photonic mode of an optical microcavity and a Majorana nanowire: a topological superconducting segment hosting Majorana bound states (MBSs) at the opposite ends. In the regime of strong light-matter coupling, it is demonstrated that the leakage of the Majorana mode into the QD opens new optica… ▽ More We study the optical properties of a hybrid device composed by a quantum dot (QD) resonantly coupled to a photonic mode of an optical microcavity and a Majorana nanowire: a topological superconducting segment hosting Majorana bound states (MBSs) at the opposite ends. In the regime of strong light-matter coupling, it is demonstrated that the leakage of the Majorana mode into the QD opens new optical transitions between polaritonic states formed due to hybridisation of material excitation with cavity photons, which leads to the reshaping of the Jaynes-Cummings ladder and can lead to the formation of a robust single-peak at cavity eigenfrequency in the emission spectrum. Moreover, weak satellite peaks in the low and high frequency regions are revealed for the distinct cases of highly isolated MBSs, overlapped MBSs and MBSs not well localized at the nanowire ends. △ Less

Submitted 15 February, 2023; v1 submitted 30 March, 2022; originally announced March 2022.

Topological charge Fano effect in multi-Weyl semimetals

Authors: W. C. Silva, W. N. Mizobata, J. E. Sanches, L. S. Ricco, I. A. Shelykh, M. de Souza, M. S. Figueira, E. Vernek, A. C. Seridonio

Abstract: We theoretically analyze the Fano interference in a single impurity multi-Weyl semimetal hybrid system and show the emergence of the topological charge Fano effect in the bulk local density of states. In multi-Weyl semimetals, the number of Fermi arcs at the system boundaries is determined by the topological charge $J$, a direct consequence of the "bulk-boundary" correspondence principle. Analogou… ▽ More We theoretically analyze the Fano interference in a single impurity multi-Weyl semimetal hybrid system and show the emergence of the topological charge Fano effect in the bulk local density of states. In multi-Weyl semimetals, the number of Fermi arcs at the system boundaries is determined by the topological charge $J$, a direct consequence of the "bulk-boundary" correspondence principle. Analogously, we find that $J$ also modulates the bulk Fano profile of the system with an embedded quantum impurity. Thus, by increasing $J$, the Fano lineshape evolves from resonant, typical for $J=1$ (single Weyl), towards antiresonant, extrapolating to the so-called hyper Weyl semimetals with $J\gg1$. Specially for the maximum case protected by the rotational symmetry $C_{2J=6}$, namely the $J=3$ (triple Weyl), which acquires asymmetric Fano profile, the Fano parameter absolute value is predicted to be $\tan(C_{2J=6})$, where $C_{2J}\equiv(360^{\circ}/2J)$ defines the rotational angle. Hence, the Fano discretization in the $J$ term introduces the topological charge Fano effect in multi-Weyl semimetals. We also suggest a transport device where we expect that the proposed Fano effect could be detected. △ Less

Submitted 24 June, 2022; v1 submitted 27 March, 2022; originally announced March 2022.

Spin-polarized Majorana zero-modes in double zigzag honeycomb nanoribbons

Authors: R. C. Bento Ribeiro, J. H. Correa, L. S. Ricco, A. C. Seridonio, M. S. Figueira

Abstract: We study the emergence of Majorana zero modes (MZMs) at the ends of a finite double zigzag honeycomb nanoribbon (zHNR). We show that a double zHNR geometry can host spin-polarized MZMs at its ends. We considered a minimal model composed by first nearest neighbor hopping, Rashba spin-orbit coupling (RSOC), p-wave superconducting pairing, and an applied external magnetic field (EMF). The energy spec… ▽ More We study the emergence of Majorana zero modes (MZMs) at the ends of a finite double zigzag honeycomb nanoribbon (zHNR). We show that a double zHNR geometry can host spin-polarized MZMs at its ends. We considered a minimal model composed by first nearest neighbor hopping, Rashba spin-orbit coupling (RSOC), p-wave superconducting pairing, and an applied external magnetic field (EMF). The energy spectrum regions with either spin up or down MZMs belong to distinct topological phase transitions characterized by their corresponding winding numbers and can be accessed by tunning the chemical potential of the nanoribbons. Hybrid systems constituted by zHNRs deposited on conventional s-wave superconductors are potential candidates for experimentally realizing the proposal. The spin's discrimination of MZMs suggests a possible route for performing topological-conventional qubit operations using Majorana spintronics. △ Less

Submitted 17 August, 2021; originally announced August 2021.

Comments: Main text (6 pages, 3 figures) + Supplemental Material (5 pages, 3 figures)

Accessing the degree of Majorana nonlocality in a quantum dot-optical microcavity system

Authors: L. S. Ricco, V. K. Kozin, A. C. Seridonio, I. A. Shelykh

Abstract: We explore the tunneling transport properties of a quantum dot embedded in an optical microcavity and coupled to a semiconductor-superconductor one-dimensional nanowire (Majorana nanowire) hosting Majorana zero modes (MZMs) at their edges. Conductance profiles reveal that strong light-matter coupling can be employed to distinguish between the cases of highly nonlocal MZMs, overlapped MZMs and MZMs… ▽ More We explore the tunneling transport properties of a quantum dot embedded in an optical microcavity and coupled to a semiconductor-superconductor one-dimensional nanowire (Majorana nanowire) hosting Majorana zero modes (MZMs) at their edges. Conductance profiles reveal that strong light-matter coupling can be employed to distinguish between the cases of highly nonlocal MZMs, overlapped MZMs and MZMs with less degree of nonlocal feature. Moreover, we show that it is possible to access the degree of Majorana nonlocality (topological quality factor) by changing the dot spectrum through photon-induced transitions tuned by an external pump applied to the microcavity. △ Less

Submitted 8 February, 2022; v1 submitted 12 May, 2021; originally announced May 2021.

Direct comparison of ARPES, STM, and quantum oscillation data for band structure determination in Sr$_2$RhO$_4$

Authors: I. Battisti, W. O. Tromp, S. Riccò, R. S. Perry, A. P. Mackenzie, A. Tamai, F. Baumberger, M. P. Allan

Abstract: Discrepancies in the low-energy quasiparticle dispersion extracted from angle resolved photoemission, scanning tunneling spectroscopy and quantum oscillation data are common and have long haunted the field of quantum matter physics. Here, we directly test the consistency of results from these three techniques by comparing data from the correlated metal Sr$_2$RhO$_4$. Using established schemes for… ▽ More Discrepancies in the low-energy quasiparticle dispersion extracted from angle resolved photoemission, scanning tunneling spectroscopy and quantum oscillation data are common and have long haunted the field of quantum matter physics. Here, we directly test the consistency of results from these three techniques by comparing data from the correlated metal Sr$_2$RhO$_4$. Using established schemes for the interpretation of the experimental data, we find good agreement for the Fermi surface topography and carrier effective masses. Hence, the apparent absence of such an agreement in other quantum materials, including the cuprates, suggests that the electronic states in these materials are of different, non-Fermi liquid like nature. Finally, we discuss the potential and challenges in extracting carrier lifetimes from photoemission and quasiparticle interference data. △ Less

Submitted 9 December, 2020; originally announced December 2020.

Journal ref: npj Quantum Mater. 5, 91 (2020)

Interaction induced hybridization of Majorana zero-modes in a coupled quantum-dot hybrid-nanowire system

Authors: L. S. Ricco, Y. Marques, J. E. Sanches, I. A. Shelykh, A. C. Seridonio

Abstract: We study the low-energy transport properties of a hybrid device composed by a native quantum dot coupled to both ends of a topological superconducting nanowire section hosting Majorana zero-modes. The account of the coupling between the dot and the farthest Majorana zero-mode allows to introduce the topological quality factor, characterizing the level of topological protection in the system. We de… ▽ More We study the low-energy transport properties of a hybrid device composed by a native quantum dot coupled to both ends of a topological superconducting nanowire section hosting Majorana zero-modes. The account of the coupling between the dot and the farthest Majorana zero-mode allows to introduce the topological quality factor, characterizing the level of topological protection in the system. We demonstrate that Coulomb interaction between the dot and the topological superconducting section leads to the onset of the additional overlap of the wavefunctions describing the Majorana zero-modes, leading to the formation of trivial Andreev bound states even for spatially well-separated Majoranas. This leads to the spoiling of the quality factor and introduces a constraint for the braiding process required to perform topological quantum computing operations. △ Less

Submitted 12 June, 2020; originally announced June 2020.

Journal ref: Phys. Rev. B 102, 165104 (2020)

Atomic frustrated impurity states in Weyl metals

Authors: W. N. Mizobata, Y. Marques, M. Penha, J. E. Sanches, L. S. Ricco, M. de Souza, I. A. Shelykh, A. C. Seridonio

Abstract: We theoretically analyze the effect of the inversion symmetry breaking on the structure of the impurity molecular states in Weyl metals. We show that for the case of a highly noncentrosymmetric Weyl metallic host, the standard picture of the alternating bonding and antibonding orbitals breaks down, and a qualitatively different frustrated atomic state emerges. This is a consequence of the pseudoga… ▽ More We theoretically analyze the effect of the inversion symmetry breaking on the structure of the impurity molecular states in Weyl metals. We show that for the case of a highly noncentrosymmetric Weyl metallic host, the standard picture of the alternating bonding and antibonding orbitals breaks down, and a qualitatively different frustrated atomic state emerges. This is a consequence of the pseudogap closing and related delicate Fano interplay between intra- and inter-impurity scattering channels. △ Less

Submitted 1 September, 2020; v1 submitted 11 May, 2020; originally announced May 2020.

Journal ref: Phys. Rev. B 102, 075120 (2020)

Topological isoconductance signatures in Majorana nanowires

Authors: L. S. Ricco, J. E. Sanches, Y. Marques, M. de Souza, M. S. Figueira, I. A. Shelykh, A. C. Seridonio

Abstract: We consider transport properties of a hybrid device composed by a quantum dot placed between normal and superconducting reservoirs, and coupled to a Majorana nanowire: a topological superconducting segment hosting Majorana zero-modes at the opposite ends. It is demonstrated that if topologically protected (nonoverlapping) Majorana zero-modes are formed in the system, zero-bias Andreev conductance… ▽ More We consider transport properties of a hybrid device composed by a quantum dot placed between normal and superconducting reservoirs, and coupled to a Majorana nanowire: a topological superconducting segment hosting Majorana zero-modes at the opposite ends. It is demonstrated that if topologically protected (nonoverlapping) Majorana zero-modes are formed in the system, zero-bias Andreev conductance through the dot exhibits isoconductance profiles with the shape depending on the spin asymmetry of the coupling between a dot and a topological superconductor. Otherwise, for the topologically trivial situation corresponding to the formation of Andreev bound states, the conductance is insensitive to the spin polarization and the isoconductance signatures disappear. This allows to propose an experimental protocol for distinguishing between isolated Majorana zero-modes and Andreev bound states. △ Less

Submitted 29 April, 2020; originally announced April 2020.

Majorana molecules and their spectral fingerprints

Authors: J. E. Sanches, L. S. Ricco, W. N. Mizobata, Y. Marques, M. de Souza, I. A. Shelykh, A. C. Seridonio

Abstract: We introduce the concept of a Majorana molecule, a topological bound state appearing in the geometry of a double quantum dot (QD) structure flanking a topological superconducting nanowire. We demonstrate that, if the Majorana bound states (MBSs) at opposite edges are probed nonlocally in a two probe experiment, the spectral density of the system reveals the so-called half-bowtie profiles, while An… ▽ More We introduce the concept of a Majorana molecule, a topological bound state appearing in the geometry of a double quantum dot (QD) structure flanking a topological superconducting nanowire. We demonstrate that, if the Majorana bound states (MBSs) at opposite edges are probed nonlocally in a two probe experiment, the spectral density of the system reveals the so-called half-bowtie profiles, while Andreev bound states (ABSs) become resolved into bonding and antibonding molecular configurations. We reveal that this effect is due to the Fano interference between pseudospin superconducting pairing channels and propose that it can be catched by a pseudospin resolved Scanning Tunneling Microscope (STM)-tip. △ Less

Submitted 1 September, 2020; v1 submitted 1 April, 2020; originally announced April 2020.

Journal ref: Phys. Rev. B 102, 075128 (2020)

Bulk and surface electronic structure of the dual-topology semimetal Pt2HgSe3

Authors: I. Cucchi, A. Marrazzo, E. Cappelli, S. Ricco, F. Y. Bruno, S. Lisi, M. Hoesch, T. K. Kim, C. Cacho, C. Besnard, E. Giannini, N. Marzari, M. Gibertini, F. Baumberger, A. Tamai

Abstract: We report high-resolution angle resolved photoemission measurements on single crystals of Pt2HgSe3 grown by high-pressure synthesis. Our data reveal a gapped Dirac nodal line whose (001)-projection separates the surface Brillouin zone in topological and trivial areas. In the non-trivial $k$-space range we find surface states with multiple saddle-points in the dispersion resulting in two van Hove s… ▽ More We report high-resolution angle resolved photoemission measurements on single crystals of Pt2HgSe3 grown by high-pressure synthesis. Our data reveal a gapped Dirac nodal line whose (001)-projection separates the surface Brillouin zone in topological and trivial areas. In the non-trivial $k$-space range we find surface states with multiple saddle-points in the dispersion resulting in two van Hove singularities in the surface density of states. Based on density functional theory calculations, we identify these surface states as signatures of a topological crystalline state which coexists with a weak topological phase. △ Less

Submitted 11 September, 2019; originally announced September 2019.

Journal ref: Phys. Rev. Lett. 124, 106402 (2020)

Band Structure and Spin-Orbital Texture of the (111)-KTaO3 Two-Dimensional Electron Gas

Authors: F. Y. Bruno, S. McKeown Walker, S. Riccò, A. de la Torre, Z. Wang, A. Tamai, T. K. Kim, M. Hoesch, M. S. Bahramy, F. Baumberger

Abstract: Two-dimensional electron gases (2DEGs) in oxides show great potential for discovering new physical phenomena and at the same time hold promise for electronic applications. In this work we use angle resolved photoemission to determine the electronic structure of a 2DEG stabilized in the (111)-oriented surface of the strong spin orbit coupling material KTaO3. Our measurements reveal multiple sub-ban… ▽ More Two-dimensional electron gases (2DEGs) in oxides show great potential for discovering new physical phenomena and at the same time hold promise for electronic applications. In this work we use angle resolved photoemission to determine the electronic structure of a 2DEG stabilized in the (111)-oriented surface of the strong spin orbit coupling material KTaO3. Our measurements reveal multiple sub-bands that emerge as a consequence of quantum confinement and form a six-fold symmetric Fermi surface. This electronic structure is well reproduced by self-consistent tight-binding supercell calculations. Based on these calculations we determine the spin and orbital texture of the 2DEG. We show that the 2DEG Fermi surface is derived from bulk J = 3/2 states and exhibits an unconventional anisotropic Rashba-like lifting of the spin-degeneracy. Spin-momentum locking holds only for high symmetry directions and a strong out-of-plane spin component renders the spin-texture three-fold symmetric. We find that the average spin-splitting on the Fermi surface is an order of magnitude larger than in SrTiO3, which should translate into an enhancement in the spin-orbitronic response of (111)-KTaO3 2DEG based devices. △ Less

Submitted 14 March, 2019; originally announced March 2019.

Comments: This is the submitted version of the published manuscript before peer-review

Journal ref: Advanced Electronic Materials, 1800860 (2019)

High-resolution photoemission on Sr2RuO4 reveals correlation-enhanced effective spin-orbit coupling and dominantly local self-energies

Authors: A. Tamai, M. Zingl, E. Rozbicki, E. Cappelli, S. Ricco, A. de la Torre, S. McKeown Walker, F. Y. Bruno, P. D. C. King, W. Meevasana, M. Shi, M. Radovic, N. C. Plumb, A. S. Gibbs, A. P. Mackenzie, C. Berthod, H. Strand, M. Kim, A. Georges, F. Baumberger

Abstract: We explore the interplay of electron-electron correlations and spin-orbit coupling in the model Fermi liquid Sr2RuO4 using laser-based angle-resolved photoemission spectroscopy. Our precise measurement of the Fermi surface confirms the importance of spin-orbit coupling in this material and reveals that its effective value is enhanced by a factor of about two, due to electronic correlations. The se… ▽ More We explore the interplay of electron-electron correlations and spin-orbit coupling in the model Fermi liquid Sr2RuO4 using laser-based angle-resolved photoemission spectroscopy. Our precise measurement of the Fermi surface confirms the importance of spin-orbit coupling in this material and reveals that its effective value is enhanced by a factor of about two, due to electronic correlations. The self-energies for the $β$ and $γ$ sheets are found to display significant angular dependence. By taking into account the multi-orbital composition of quasiparticle states, we determine self-energies associated with each orbital component directly from the experimental data. This analysis demonstrates that the perceived angular dependence does not imply momentum-dependent many-body effects, but arises from a substantial orbital mixing induced by spin-orbit coupling. A comparison to single-site dynamical mean-field theory further supports the notion of dominantly local orbital self-energies, and provides strong evidence for an electronic origin of the observed non-linear frequency dependence of the self-energies, leading to `kinks' in the quasiparticle dispersion of Sr2RuO4. △ Less

Submitted 7 May, 2019; v1 submitted 16 December, 2018; originally announced December 2018.

Comments: PRX accepted

Journal ref: Phys. Rev. X 9, 021048 (2019)

Spin-dependent zero-bias peak in a hybrid nanowire-quantum dot system: Distinguishing isolated Majorana fermions from Andreev bound states

Authors: L. S. Ricco, M. de Souza, M. S. Figueira, I. A. Shelykh, A. C. Seridonio

Abstract: Hybrid system composed by a semiconducting nanowire with proximity-induced superconductivity and a quantum dot at the end working as spectrometer was recently used to quantify the so-called degree of Majorana nonlocality [Deng et al., Phys.Rev.B, 98, 085125 (2018)]. Here we demonstrate that spin-resolved density of states of the dot responsible for zero-bias conductance peak strongly depends on th… ▽ More Hybrid system composed by a semiconducting nanowire with proximity-induced superconductivity and a quantum dot at the end working as spectrometer was recently used to quantify the so-called degree of Majorana nonlocality [Deng et al., Phys.Rev.B, 98, 085125 (2018)]. Here we demonstrate that spin-resolved density of states of the dot responsible for zero-bias conductance peak strongly depends on the separation between the Majorana bound states (MBSs) and their relative couplings with the dot and investigate how the charging energy affects the spectrum of the system in the distinct scenarios of Majorana nonlocality (topological quality). Our findings suggest that spin-resolved spectroscopy of the local density of states of the dot can be used as a powerful tool for discriminating between different scenarios of the emergence of zero-bias conductance peak. △ Less

Submitted 2 May, 2019; v1 submitted 26 November, 2018; originally announced November 2018.

Journal ref: Phys. Rev. B 99, 155159 (2019)

Persistence of antiferromagnetic order upon La substitution in the $4d^4$ Mott insulator Ca$_2$RuO$_4$

Authors: D. Pincini, S. Boseggia, R. Perry, M. J. Gutmann, S. Riccò, L. S. I. Veiga, C. D. Dashwood, S. P. Collins, G. Nisbet, A. Bombardi, D. G. Porter, F. Baumberger, A. T. Boothroyd, D. F. McMorrow

Abstract: The chemical and magnetic structures of the series of compounds Ca$_{2-x}$La$_x$RuO$_4$ [$x = 0$, $0.05(1)$, $0.07(1)$, $0.12(1)$] have been investigated using neutron diffraction and resonant elastic x-ray scattering. Upon La doping, the low temperature S-Pbca space group of the parent compound is retained in all insulating samples [$x\leq0.07(1)$], but with significant changes to the atomic posi… ▽ More The chemical and magnetic structures of the series of compounds Ca$_{2-x}$La$_x$RuO$_4$ [$x = 0$, $0.05(1)$, $0.07(1)$, $0.12(1)$] have been investigated using neutron diffraction and resonant elastic x-ray scattering. Upon La doping, the low temperature S-Pbca space group of the parent compound is retained in all insulating samples [$x\leq0.07(1)$], but with significant changes to the atomic positions within the unit cell. These changes can be characterised in terms of the local RuO$_6$ octahedral coordination: with increasing doping the structure, crudely speaking, evolves from an orthorhombic unit cell with compressed octahedra to a quasi-tetragonal unit cell with elongated ones. The magnetic structure on the other hand, is found to be robust, with the basic $k=(0,0,0)$, $b$-axis antiferromagnetic order of the parent compound preserved below the critical La doping concentration of $x\approx0.11$. The only effects of La doping on the magnetic structure are to suppress the A-centred mode, favouring the B mode instead, and to reduce the Néel temperature somewhat. Our results are discussed with reference to previous experimental reports on the effects of cation substitution on the $d^4$ Mott insulator Ca$_2$RuO$_4$, as well as with regard to theoretical studies on the evolution of its electronic and magnetic structure. In particular, our results rule out the presence of a proposed ferromagnetic phase, and suggest that the structural effects associated with La substitution play an important role in the physics of the system. △ Less

Submitted 28 June, 2018; v1 submitted 15 May, 2018; originally announced May 2018.

Comments: 10 pages, 9 figures

Journal ref: Phys. Rev. B 98, 014429 (2018)

In-situ strain-tuning of the metal-insulator-transition of Ca$_{2}$RuO$_{4}$ in angle-resolved photoemission experiments

Authors: S. Riccò, M. Kim, A. Tamai, S. McKeown Walker, F. Y. Bruno, I. Cucchi, E. Cappelli, C. Besnard, T. K. Kim, P. Dudin, M. Hoesch, M. Gutmann, A. Georges, R. S. Perry, F. Baumberger

Abstract: We report the evolution of the $k$-space electronic structure of lightly doped bulk Ca$_{2}$RuO$_{4}$ with uniaxial strain. Using ultrathin plate-like crystals, we achieve strain levels up to $-4.1\%$, sufficient to suppress the Mott phase and access the previously unexplored metallic state at low temperature. Angle-resolved photoemission experiments performed while tuning the uniaxial strain reve… ▽ More We report the evolution of the $k$-space electronic structure of lightly doped bulk Ca$_{2}$RuO$_{4}$ with uniaxial strain. Using ultrathin plate-like crystals, we achieve strain levels up to $-4.1\%$, sufficient to suppress the Mott phase and access the previously unexplored metallic state at low temperature. Angle-resolved photoemission experiments performed while tuning the uniaxial strain reveal that metallicity emerges from a marked redistribution of charge within the Ru $t_{2g}$ shell, accompanied by a sudden collapse of the spectral weight in the lower Hubbard band and the emergence of a well defined Fermi surface which is devoid of pseudogaps. Our results highlight the profound roles of lattice energetics and of the multiorbital nature of Ca$_{2}$RuO$_{4}$ in this archetypal Mott transition and open new perspectives for spectroscopic measurements. △ Less

Submitted 24 October, 2018; v1 submitted 1 March, 2018; originally announced March 2018.

Comments: To appear in Nature Communications

Journal ref: Nature Communications 9, 4535 (2018)

Majorana oscillations modulated by Fano interference and dregree of non-locality in a topological superconducting nanowire-quantum dot system

Authors: L. S. Ricco, V. L. Campo Jr., I. A. Shelykh, A. C. Seridonio

Abstract: We explore theoretically the influence of Fano interference in the so-called Majorana oscillations in a T-shaped hybrid setup formed by a quantum dot (QD) placed between conducting leads and side-coupled to a topological superconducting nanowire (TSNW) hosting zero-energy Majorana bound states (MBSs) at the ends. Differential conductance as a function of the external magnetic field reveals oscilla… ▽ More We explore theoretically the influence of Fano interference in the so-called Majorana oscillations in a T-shaped hybrid setup formed by a quantum dot (QD) placed between conducting leads and side-coupled to a topological superconducting nanowire (TSNW) hosting zero-energy Majorana bound states (MBSs) at the ends. Differential conductance as a function of the external magnetic field reveals oscillatory behavior. Both the shape and amplitude of the oscillations depend on the bias-voltage, degree of MBSs non-locality and Fano parameter of the system determining the regime of interference. When the latter is such that direct lead-lead path dominates over lead-QD-lead path and the bias is tuned in resonance with QD zero-energy, pronounced fractional Fano-like resonances are observed around zero-bias for highly non-local geometries. Further, the conductance profiles as a function of both bias-voltage and QD energy level display "bowtie" and "diamond" shapes, in qualitative agreement with both previous theoretical and experimental works. These findings ensure that our proposal can be used to estimate the degree of MBS non-locality, thus allowing to investigate their topological properties. △ Less

Submitted 30 September, 2018; v1 submitted 20 February, 2018; originally announced February 2018.

Journal ref: Phys. Rev. B 98, 075142 (2018)

Antibonding Ground state of Adatom Molecules in Bulk Dirac Semimetals

Authors: Y. Marques, A. E. Obispo, L. S. Ricco, M. de Souza, I. A. Shelykh, A. C. Seridonio

Abstract: The ground state of the diatomic molecules in nature is inevitably bonding, and its first excited state is antibonding. We demonstrate theoretically that, for a pair of distant adatoms placed buried in three-dimensional-Dirac semimetals, this natural order of the states can be reversed and an antibonding ground state occurs at the lowest energy of the so-called bound states in the continuum. We pr… ▽ More The ground state of the diatomic molecules in nature is inevitably bonding, and its first excited state is antibonding. We demonstrate theoretically that, for a pair of distant adatoms placed buried in three-dimensional-Dirac semimetals, this natural order of the states can be reversed and an antibonding ground state occurs at the lowest energy of the so-called bound states in the continuum. We propose an experimental protocol with the use of a scanning tunneling microscope tip to visualize the topographic map of the local density of states on the surface of the system to reveal the emerging physics. △ Less

Submitted 18 July, 2017; v1 submitted 25 May, 2017; originally announced May 2017.

Journal ref: Phys. Rev. B 96, 041112 (2017)

Encrypting Majorana Fermions-qubits as Bound States in the Continuum

Authors: L. H. Guessi, F. A. Dessotti, Y. Marques, L. S. Ricco, G. M. Pereira, P. Menegasso, M. de Souza, A. C. Seridonio

Abstract: We theoretically investigate a topological Kitaev chain connected to a double quantum-dot (QD) setup hybridized with metallic leads. In this system we observe the emergence of two striking phenomena: (i) a decrypted Majorana fermion (MF) qubit recorded over a single QD, which is detectable by means of conductance measurements due to the asymmetrical MF-qubit leaked state into the QDs; (ii) an encr… ▽ More We theoretically investigate a topological Kitaev chain connected to a double quantum-dot (QD) setup hybridized with metallic leads. In this system we observe the emergence of two striking phenomena: (i) a decrypted Majorana fermion (MF) qubit recorded over a single QD, which is detectable by means of conductance measurements due to the asymmetrical MF-qubit leaked state into the QDs; (ii) an encrypted qubit recorded in both QDs when the leakage is symmetrical. In such a regime, we have a cryptographylike manifestation, since the MF qubit becomes bound states in the continuum, which is not detectable in conductance experiments. △ Less

Submitted 18 July, 2017; v1 submitted 29 March, 2017; originally announced March 2017.

Journal ref: Phys. Rev. B 96, 041114 (2017)

Isolating Majorana fermions with finite Kitaev nanowires and temperature: the universality of the zero-bias conductance

Authors: V. L. Campo Jr, L. S. Ricco, A. C. Seridonio

Abstract: The zero-bias peak (ZBP) is understood as the definite signature of a Majorana bound state (MBS) when attached to a semi-infinite Kitaev nanowire (KNW) nearby zero temperature. However, such characteristics concerning the realization of the KNW constitute a profound experimental challenge. We explore theoretically a QD connected to a topological KNW of finite size at non-zero temperatures and show… ▽ More The zero-bias peak (ZBP) is understood as the definite signature of a Majorana bound state (MBS) when attached to a semi-infinite Kitaev nanowire (KNW) nearby zero temperature. However, such characteristics concerning the realization of the KNW constitute a profound experimental challenge. We explore theoretically a QD connected to a topological KNW of finite size at non-zero temperatures and show that overlapped MBSs of the wire edges can become effectively decoupled from each other and the characteristic ZBP can be fully recovered if one tunes the system into the leaked Majorana fermion fixed point. At very low temperatures, the MBSs become strongly coupled similarly to what happens in the Kondo effect. We derive universal features of the conductance as a function of the temperature and the relevant crossover temperatures. Our findings offer additional guides to identify signatures of MBSs in solid state setups. △ Less

Submitted 28 March, 2017; originally announced March 2017.

Journal ref: Phys. Rev. B 96, 045135 (2017)

Atomically precise lateral modulation of a two-dimensional electron liquid in anatase TiO2 thin films

Authors: Z. Wang, Z. Zhong, S. McKeown Walker, Z. Ristic, J. -Z. Ma, F. Y. Bruno, S. Ricco, G. Sangiovanni, G. Eres, N. C. Plumb, L. Patthey, M. Shi, J. Mesot, F. Baumberger, M. Radovic

Abstract: Engineering the electronic band structure of two-dimensional electron liquids (2DELs) confined at the surface or interface of transition metal oxides is key to unlocking their full potential. Here we describe a new approach to tailoring the electronic structure of an oxide surface 2DEL demonstrating the lateral modulation of electronic states with atomic scale precision on an unprecedented length… ▽ More Engineering the electronic band structure of two-dimensional electron liquids (2DELs) confined at the surface or interface of transition metal oxides is key to unlocking their full potential. Here we describe a new approach to tailoring the electronic structure of an oxide surface 2DEL demonstrating the lateral modulation of electronic states with atomic scale precision on an unprecedented length scale comparable to the Fermi wavelength. To this end, we use pulsed laser deposition to grow anatase TiO2 films terminated by a (1 x 4) in-plane surface reconstruction. Employing photo-stimulated chemical surface doping we induce 2DELs with tunable carrier densities that are confined within a few TiO2 layers below the surface. Subsequent in-situ angle resolved photoemission experiments demonstrate that the (1 x 4) surface reconstruction provides a periodic lateral perturbation of the electron liquid. This causes strong backfolding of the electronic bands, opening of unidirectional gaps and a saddle point singularity in the density of states near the chemical potential. △ Less

Submitted 1 March, 2017; originally announced March 2017.

Electronic structure of buried LaNiO3 layers in (111)-oriented LaNiO3/LaMnO3 superlattices probed by soft x-ray ARPES

Authors: F. Y. Bruno, M. Gibert, S. McKeown Walker, O. E. Peil, A. de la Torre, S. Riccò, Z. Wang, S. Catalano, A. Tamai, F. Bisti, V. N. Strocov, J-M Triscone, F. Baumberger

Abstract: Taking advantage of the large electron escape depth of soft x-ray angle resolved photoemission spectroscopy we report electronic structure measurements of (111)-oriented [LaNiO3/LaMnO3] superlattices and LaNiO3 epitaxial films. For thin films we observe a 3D Fermi surface with an electron pocket at the Brillouin zone center and hole pockets at the zone vertices. Superlattices with thick nickelate… ▽ More Taking advantage of the large electron escape depth of soft x-ray angle resolved photoemission spectroscopy we report electronic structure measurements of (111)-oriented [LaNiO3/LaMnO3] superlattices and LaNiO3 epitaxial films. For thin films we observe a 3D Fermi surface with an electron pocket at the Brillouin zone center and hole pockets at the zone vertices. Superlattices with thick nickelate layers present a similar electronic structure. However, as the thickness of the LaNiO3 is reduced the superlattices become insulating. These heterostructures do not show a marked redistribution of spectral weight in momentum space but exhibit a pseudogap of 50 meV. △ Less

Submitted 25 November, 2016; originally announced November 2016.

Journal ref: APL Mater. 5, 016101 (2017)

Tuning of heat and charge transport by Majorana fermions

Authors: L. S. Ricco, F. A. Dessotti, I. A. Shelykh, M. S. Figueira, A. C. Seridonio

Abstract: We investigate theoretically thermal and electrical conductances for the system consisting of a quantum dot (QD) connected both to a pair of Majorana fermions residing the edges of a Kitaev wire and two metallic leads. We demonstrate that both quantities reveal pronounced resonances, whose positions can be controlled by tuning of an asymmetry of the couplings of the QD and a pair of MFs. Similar b… ▽ More We investigate theoretically thermal and electrical conductances for the system consisting of a quantum dot (QD) connected both to a pair of Majorana fermions residing the edges of a Kitaev wire and two metallic leads. We demonstrate that both quantities reveal pronounced resonances, whose positions can be controlled by tuning of an asymmetry of the couplings of the QD and a pair of MFs. Similar behavior is revealed for the thermopower, Wiedemann-Franz law and dimensionless thermoelectric figure of merit. The considered geometry can thus be used as a tuner of heat and charge transport assisted by MFs. △ Less

Submitted 13 February, 2018; v1 submitted 14 November, 2016; originally announced November 2016.

Journal ref: Scientific Reports volume 8, Article number: 2790 (2018)

Realization of anomalous multiferroicity in free-standing graphene with magnetic adatoms

Authors: Y. Marques, L. S. Ricco, F. A. Dessotti, R. S. Machado, I. A. Shelykh, M. de Souza, A. C. Seridonio

Abstract: It is generally believed that free-standing graphene does not demonstrate any ferroic properties. In the present work we revise this statement and show that single graphene sheet with a pair of magnetic adatoms can be driven into ferroelectric (FE) and multiferroic (MF) phases by tuning the Dirac cones slope. The transition into the FE phase occurs gradually, but an anomalous MF phase appears abru… ▽ More It is generally believed that free-standing graphene does not demonstrate any ferroic properties. In the present work we revise this statement and show that single graphene sheet with a pair of magnetic adatoms can be driven into ferroelectric (FE) and multiferroic (MF) phases by tuning the Dirac cones slope. The transition into the FE phase occurs gradually, but an anomalous MF phase appears abruptly by means of a Quantum Phase Transition. Our findings suggest that such features should exist in graphene recently investigated by Scanning Tunneling Microscopy (Science 352, 437 (2016)). △ Less

Submitted 14 November, 2016; v1 submitted 15 June, 2016; originally announced June 2016.

Journal ref: Phys. Rev. B 94, 205119 (2016)

Unveiling Majorana Quasiparticles by a Quantum Phase Transition: Proposal of a Current Switch

Authors: F. A. Dessotti, L. S. Ricco, Y. Marques, L. H. Guessi, M. Yoshida, M. S. Figueira, M. de Souza, Pasquale Sodano, A. C. Seridonio

Abstract: We propose a theoretical approach based on an interferometer composed by two quantum dots asymmetrically coupled to isolated Majorana quasiparticles (MQPs), lying on the edges of two topological Kitaev chains, respectively via couplings $(t+Δ)$ and $(Δ-t)$. This setup enables us to probe MQPs in a quite distinct way from the zero-bias peak feature. Most importantly, the system behaves as a current… ▽ More We propose a theoretical approach based on an interferometer composed by two quantum dots asymmetrically coupled to isolated Majorana quasiparticles (MQPs), lying on the edges of two topological Kitaev chains, respectively via couplings $(t+Δ)$ and $(Δ-t)$. This setup enables us to probe MQPs in a quite distinct way from the zero-bias peak feature. Most importantly, the system behaves as a current switch made by two distinct paths: (i) for the upper dot connected to both chains, the device perceives both MQPs as an ordinary fermion and the current crosses solely the lower dot, since current in the upper dot is prevented due to the presence of the superconducting gap; and (ii) by suppressing slightly the hybridization of the upper dot with one chain, the current is abruptly switched to flow through this dot, once a trapped electron as a bound state in the continuum (BIC) (Phys. Rev. B 93, 165116 (2016)) appears in the lower dot. Such a current switch between upper and lower dots characterizes the Quantum Phase Transition (QPT) proposed here, being the ratio $t/Δ$ the control parameter of the transition. This QPT is associated with a change from an ordinary fermionic excitation regime to a MQP in the interferometer, which enables not only the fundamental revealing of MQPs, but also yields a current switch assisted by them. △ Less

Submitted 14 November, 2016; v1 submitted 13 May, 2016; originally announced May 2016.

Journal ref: Phys. Rev. B 94, 125426 (2016)

Fermi arcs and their topological character in the candidate type-II Weyl semimetal MoTe2

Authors: A. Tamai, Q. S. Wu, I. Cucchi, F. Y. Bruno, S. Ricco, T. K. Kim, M. Hoesch, C. Barreteau, E. Giannini, C. Bernard, A. A. Soluyanov, F. Baumberger

Abstract: We report a combined experimental and theoretical study of the candidate type-II Weyl semimetal MoTe2. Using laser-based angle-resolved photoemission we resolve multiple distinct Fermi arcs on the inequivalent top and bottom (001) surfaces. All surface states observed experimentally are reproduced by an electronic structure calculation for the experimental crystal structure that predicts a topolog… ▽ More We report a combined experimental and theoretical study of the candidate type-II Weyl semimetal MoTe2. Using laser-based angle-resolved photoemission we resolve multiple distinct Fermi arcs on the inequivalent top and bottom (001) surfaces. All surface states observed experimentally are reproduced by an electronic structure calculation for the experimental crystal structure that predicts a topological Weyl semimetal state with 8 type-II Weyl points. We further use systematic electronic structure calculations simulating different Weyl point arrangements to discuss the robustness of the identified Weyl semimetal state and the topological character of Fermi arcs in MoTe2. △ Less

Submitted 21 July, 2016; v1 submitted 27 April, 2016; originally announced April 2016.

Comments: revised version, PRX accepted

Journal ref: Phys. Rev. X 6, 031021 (2016)

Observation of Large Topologically Trivial Fermi-Arcs in the Candidate Type-II Weyl Semimetal WTe2

Authors: F. Y. Bruno, A. Tamai, Q. S. Wu, I. Cucchi, C. Barreteau, A. de la Torre, S. McKeown Walker, S. Riccò, Z. Wang, T. K. Kim, M. Hoesch, M. Shi, N. C. Plumb, E. Giannini, A. A. Soluyanov, F. Baumberger

Abstract: We report angle-resolved photoemission experiments resolving the distinct electronic structure of the inequivalent top and bottom (001) surfaces of WTe2. On both surfaces, we identify a surface state that forms a large Fermi-arc emerging out of the bulk electron pocket. Using surface electronic structure calculations, we show that these Fermi arcs are topologically trivial and that their existence… ▽ More We report angle-resolved photoemission experiments resolving the distinct electronic structure of the inequivalent top and bottom (001) surfaces of WTe2. On both surfaces, we identify a surface state that forms a large Fermi-arc emerging out of the bulk electron pocket. Using surface electronic structure calculations, we show that these Fermi arcs are topologically trivial and that their existence is independent of the presence of type-II Weyl points in the bulk band structure. This implies that the observation of surface Fermi arcs alone does not allow the identification of WTe2 as a topological Weyl semimetal. We further use the identification of the two different surfaces to clarify the number of Fermi surface sheets in WTe2. △ Less

Submitted 12 September, 2016; v1 submitted 8 April, 2016; originally announced April 2016.

Comments: Accepted in Physical Review B Rapid Communication on 16 Aug 2016

Journal ref: Phys. Rev. B 94, 121112 (2016)

Absence of Giant Spin Splitting in the Two-Dimensional Electron Liquid at the Surface of SrTiO$_3$ (001)

Authors: S. McKeown Walker, S Riccò, F. Y. Bruno, A. de la Torre, A. Tamai, E. Golias, A. Varykhalov, D. Marchenko, M. Hoesch, M. S. Bahramy, P. D. C. King, J. Sánchez-Barriga, F. Baumberger

Abstract: We reinvestigate the putative giant spin splitting at the surface of SrTiO$_3$ reported by Santander-Syro $et~al.$ [Nature Mat. 13, 1085 (2014)]. Our spin- and angle-resolved photoemission experiments on (001) oriented surfaces supporting a two-dimensional electron liquid with high carrier density show no detectable spin polarization in the photocurrent. We demonstrate that this result excludes a… ▽ More We reinvestigate the putative giant spin splitting at the surface of SrTiO$_3$ reported by Santander-Syro $et~al.$ [Nature Mat. 13, 1085 (2014)]. Our spin- and angle-resolved photoemission experiments on (001) oriented surfaces supporting a two-dimensional electron liquid with high carrier density show no detectable spin polarization in the photocurrent. We demonstrate that this result excludes a giant spin splitting while it is fully consistent with the unconventional Rashba-like splitting seen in band structure calculations that reproduce the experimentally observed ladder of quantum confined subbands. △ Less

Submitted 1 March, 2016; originally announced March 2016.

Journal ref: Phys. Rev. B 93, 245143 (2016)

Decay of bound states in the continuum of Majorana fermions induced by vacuum fluctuations: Proposal of qubit technology

Authors: L. S. Ricco, Y. Marques, F. A. Dessotti, R. S. Machado, M. de Souza, A. C. Seridonio

Abstract: We report on a theoretical investigation of the interplay between vacuum fluctuations, Majorana quasiparticles (MQPs) and bound states in the continuum (BICs) by proposing a new venue for qubit storage.BICs emerge due to quantum interference processes as the Fano effect and, since such a mechanism is unbalanced, these states decay as regular into the continuum. Such fingerprints identify BICs in g… ▽ More We report on a theoretical investigation of the interplay between vacuum fluctuations, Majorana quasiparticles (MQPs) and bound states in the continuum (BICs) by proposing a new venue for qubit storage.BICs emerge due to quantum interference processes as the Fano effect and, since such a mechanism is unbalanced, these states decay as regular into the continuum. Such fingerprints identify BICs in graphene as we have discussed in detail in Phys. Rev. B 92, 245107 and 045409 (2015). Here by considering two semi-infinite Kitaev chains within the topological phase, coupled to a quantum dot (QD) hybridized with leads, we show the emergence of a novel type of BICs, in which MQPs are trapped. As the MQPs of these chains far apart build a delocalized fermion and qubit, we identify that the decay of these BICs is not connected to Fano and it occurs when finite fluctuations are observed in the vacuum composed by electron pairs for this qubit. From the experimental point of view, we also show that vacuum fluctuations can be induced just by changing the chain-dot couplings from symmetric to asymmetric. Hence, we show how to perform the qubit storage within two delocalized BICs of MQPs and to access it when the vacuum fluctuates by means of a complete controllable way in quantum transport experiments. △ Less

Submitted 16 April, 2016; v1 submitted 8 December, 2015; originally announced December 2015.

Comments: New version

Journal ref: Phys. Rev. B 93, 165116 (2016)

Effect of Interdots Electronic Repulsion in the Majorana Signature for a Double Dot Interferometer

Authors: L. S. Ricco, Y. Marques, F. A. Dessotti, M. de Souza, A. C. Seridonio

Abstract: We investigate theoretically the features of the Majorana hallmark in the presence of Coulomb repulsion between two quantum dots describing a spinless Aharonov-Bohm-like interferometer, where one of the dots is strongly coupled to a Kitaev wire within the topological phase. Such a system has been originally proposed without Coulomb interaction in J. of Appl. Phys. 116, 173701 (2014). Our findings… ▽ More We investigate theoretically the features of the Majorana hallmark in the presence of Coulomb repulsion between two quantum dots describing a spinless Aharonov-Bohm-like interferometer, where one of the dots is strongly coupled to a Kitaev wire within the topological phase. Such a system has been originally proposed without Coulomb interaction in J. of Appl. Phys. 116, 173701 (2014). Our findings reveal that for dots in resonance, the ratio between the strength of Coulomb repulsion and the dot-wire coupling changes the width of the Majorana zero-bias peak for both Fano regimes studied, indicating thus that the electronic interdots correlation influences the Majorana state lifetime in the dot hybridized with the wire. Moreover, for the off-resonance case, the swap between the energy levels of the dots also modifies the width of the Majorana peak, which does not happen for the noninteracting case. The results obtained here can guide experimentalists that pursuit a way of revealing Majorana signatures. △ Less

Submitted 11 December, 2015; v1 submitted 3 November, 2015; originally announced November 2015.

Journal ref: Physica E 78, 25-30 (2016)

Quantum phase transition triggering magnetic BICs in graphene

Authors: L. H. Guessi, Y. Marques, R. S. Machado, K. Kristinsson, L. S. Ricco, I. A. Shelykh, M. S. Figueira, M. de Souza, A. C. Seridonio

Abstract: Graphene hosting a pair of collinear adatoms in the phantom atom configuration has pseudogap with cubic scaling on energy, $Δ\propto|\varepsilon|^{3}$ which leads to the appearance of spin-degenerate bound states in the continuum (BICs) [Phys. Rev. B 92, 045409 (2015)]. In the case when adatoms are locally coupled to a single carbon atom the pseudogap scales linearly with energy, which prevents th… ▽ More Graphene hosting a pair of collinear adatoms in the phantom atom configuration has pseudogap with cubic scaling on energy, $Δ\propto|\varepsilon|^{3}$ which leads to the appearance of spin-degenerate bound states in the continuum (BICs) [Phys. Rev. B 92, 045409 (2015)]. In the case when adatoms are locally coupled to a single carbon atom the pseudogap scales linearly with energy, which prevents the formation of BICs. In this Letter, we explore the effects of non-local coupling characterized by the Fano factor of interference $q_{0},$ tunable by changing the slope of the Dirac cones in the graphene band-structure. We demonstrate that three distinct regimes can be identified: i) for $q_{0}<q_{c1}$ (critical point) a mixed pseudogap $Δ\propto|\varepsilon|,|\varepsilon|^{2}$ appears yielding a phase with spin-degenerate BICs; ii) near $q_{0}=q_{c1}$ when $Δ\propto|\varepsilon|^{2}$ the system undergoes a quantum phase transition in which the new phase is characterized by magnetic BICs and iii) at a second critical value $q_{0}>q_{c2}$ the cubic scaling of the pseudogap with energy $Δ\propto|\varepsilon|^{3}$ characteristic to the phantom atom configuration is restored and the phase with non-magnetic BICs is recovered. The phase with magnetic BICs can be described in terms of an effective intrinsic exchange field of ferromagnetic nature between the adatoms mediated by graphene monolayer. We thus propose a new type of quantum phase transition resulting from the competition between the states characterized by spin-degenerate and magnetic BICs. △ Less

Submitted 8 December, 2015; v1 submitted 13 July, 2015; originally announced July 2015.

Journal ref: Phys. Rev. B 92, 245107 (2015)

Tailoring the nature and strength of electron-phonon interactions in the SrTiO$_3$(001) two-dimensional electron liquid

Authors: Z. Wang, S. McKeown Walker, A. Tamai, Y. Wang, Z. Ristic, F. Y. Bruno, A. de la Torre, S. Riccò, N. C. Plumb, M. Shi, P. Hlawenka, J. Sánchez-Barriga, A. Varykhalov, T. K. Kim, M. Hoesch, P. D. C. King, W. Meevasana, U. Diebold, J. Mesot, B. Moritz, T. P. Devereaux, M. Radovic, F. Baumberger

Abstract: Surfaces and interfaces offer new possibilities for tailoring the many-body interactions that dominate the electrical and thermal properties of transition metal oxides. Here, we use the prototypical two-dimensional electron liquid (2DEL) at the SrTiO$_3$(001) surface to reveal a remarkably complex evolution of electron-phonon coupling with the tunable carrier density of this system. At low density… ▽ More Surfaces and interfaces offer new possibilities for tailoring the many-body interactions that dominate the electrical and thermal properties of transition metal oxides. Here, we use the prototypical two-dimensional electron liquid (2DEL) at the SrTiO$_3$(001) surface to reveal a remarkably complex evolution of electron-phonon coupling with the tunable carrier density of this system. At low density, where superconductivity is found in the analogous 2DEL at the LaAlO$_3$/SrTiO$_3$ interface, our angle-resolved photoemission data show replica bands separated by 100\,meV from the main bands. This is a hallmark of a coherent polaronic liquid and implies strong long-range coupling to a single longitudinal optical phonon mode. In the overdoped regime the preferential coupling to this mode decreases and the 2DEL undergoes a crossover to a more conventional metallic state with weaker short-range electron-phonon interaction. These results place constraints on the theoretical description of superconductivity and allow for a unified understanding of the transport properties in SrTiO$_3$-based 2DELs. △ Less

Submitted 19 February, 2016; v1 submitted 3 June, 2015; originally announced June 2015.

Journal ref: Nature Materials (2016)

Collapse of the Mott gap and emergence of a nodal liquid in lightly doped Sr$_2$IrO$_4$

Authors: A. de la Torre, S. McKeown Walker, F. Y. Bruno, S. Ricco, Z. Wang, I. Gutierrez Lezama, G. Scheerer, G. Giriat, D. Jaccard, C. Berthod, T. K. Kim, M. Hoesch, E. C. Hunter, R. S. Perry, A. Tamai, F. Baumberger

Abstract: Superconductivity in underdoped cuprates emerges from an unusual electronic state characterised by nodal quasiparticles and an antinodal pseudogap. The relation between this state and superconductivity is intensely studied but remains controversial. The discrimination between competing theoretical models is hindered by a lack of electronic structure data from related doped Mott insulators. Here we… ▽ More Superconductivity in underdoped cuprates emerges from an unusual electronic state characterised by nodal quasiparticles and an antinodal pseudogap. The relation between this state and superconductivity is intensely studied but remains controversial. The discrimination between competing theoretical models is hindered by a lack of electronic structure data from related doped Mott insulators. Here we report the doping evolution of the Heisenberg antiferromagnet Sr$_2$IrO$_4$, a close analogue to underdoped cuprates. We demonstrate that metallicity emerges from a rapid collapse of the Mott gap with doping, resulting in lens-like Fermi contours rather than disconnected Fermi arcs as observed in cuprates. Intriguingly though, the emerging electron liquid shows nodal quasiparticles with an antinodal pseudogap and thus bares strong similarities with underdoped cuprates. We conclude that anisotropic pseudogaps are a generic property of two-dimensional doped Mott insulators rather than a unique hallmark of cuprate high-temperature superconductivity. △ Less

Submitted 1 June, 2015; originally announced June 2015.

Journal ref: Phys. Rev. Lett. 115, 176402 (2015)

Catching the Bound States in the Continuum of a Phantom Atom in Graphene

Authors: L. H. Guessi, R. S. Machado, Y. Marques, L. S. Ricco, K. Kristinsson, M. Yoshida, I. A. Shelykh, M. de Souza, A. C. Seridonio

Abstract: We explore theoretically the formation of bound states in the continuum (BICs) in graphene hosting two collinear adatoms situated at different sides of the sheet and at the center of the hexagonal cell, where a phantom atom of a fictitious lattice emulates the six carbons of the cell. We verify that in this configuration the local density of states (LDOS) near the Dirac points exhibits two charact… ▽ More We explore theoretically the formation of bound states in the continuum (BICs) in graphene hosting two collinear adatoms situated at different sides of the sheet and at the center of the hexagonal cell, where a phantom atom of a fictitious lattice emulates the six carbons of the cell. We verify that in this configuration the local density of states (LDOS) near the Dirac points exhibits two characteristic features: i) the cubic dependence on energy instead of the linear one for graphene as found in New J. Phys. 16, 013045 (2014) and ii) formation of BICs as aftermath of a Fano destructive interference assisted by the Coulomb correlations in the adatoms. For the geometry where adatoms are collinear to carbon atoms, we report absence of BICs. △ Less

Submitted 9 July, 2015; v1 submitted 4 March, 2015; originally announced March 2015.

Journal ref: Physical Review B 92, 045409 (2015)

Fano fingerprints of Majoranas in Kitaev dimers of superconducting adatoms

Authors: F. A. Dessotti, L. S. Ricco, Y. Marques, R. S. Machado, L. H. Guessi, M. S. Figueira, M. de Souza, A. C. Seridonio

Abstract: We investigate theoretically a Fano interferometer composed by STM and AFM tips close to a Kitaev dimer of superconducting adatoms, in which the adatom placed under the AFM tip, encloses a pair of Majorana fermions (MFs). For the binding energy $Δ$ of the Cooper pair delocalized into the adatoms under the tips coincident with the tunneling amplitude $t$ between them, namely $Δ$ = $t$, we find that… ▽ More We investigate theoretically a Fano interferometer composed by STM and AFM tips close to a Kitaev dimer of superconducting adatoms, in which the adatom placed under the AFM tip, encloses a pair of Majorana fermions (MFs). For the binding energy $Δ$ of the Cooper pair delocalized into the adatoms under the tips coincident with the tunneling amplitude $t$ between them, namely $Δ$ = $t$, we find that only one MF beneath the AFM tip hybridizes with the adatom coupled to the STM tips. As a result, a gate invariance feature emerges: the Fano profile of the transmittance rises as an invariant quantity depending upon the STM tips Fermi energy, due to the symmetric swap in the gate potential of the AFM tip. △ Less

Submitted 18 May, 2016; v1 submitted 2 March, 2015; originally announced March 2015.

Comments: Online version published in Physica E

Probing the Antisymmetric Fano Interference Assisted by a Majorana Fermion

Authors: F. A. Dessotti, L. S. Ricco, M. de Souza, F. M. Souza, A. C. Seridonio

Abstract: As the Fano effect is an interference phenomenon where tunneling paths compete for the electronic transport, it becomes a probe to catch fingerprints of Majorana fermions lying on condensed matter systems. In this work we benefit of this mechanism by proposing as a route for that an Aharonov-Bohm-like interferometer composed by two quantum dots, being one of them coupled to a Majorana bound state,… ▽ More As the Fano effect is an interference phenomenon where tunneling paths compete for the electronic transport, it becomes a probe to catch fingerprints of Majorana fermions lying on condensed matter systems. In this work we benefit of this mechanism by proposing as a route for that an Aharonov-Bohm-like interferometer composed by two quantum dots, being one of them coupled to a Majorana bound state, which is attached to one of the edges of a semi-infinite Kitaev wire within the topological phase. By changing the Fermi energy of the leads and the symmetric detuning of the levels for the dots, we show that opposing Fano regimes result in a transmittance characterized by distinct conducting and insulating regions, which are fingerprints of an isolated Majorana quasiparticle. Furthermore, we show that the maximum fluctuation of the transmittance as a function of the detuning is half for a semi-infinite wire, while it corresponds to the unity for a finite system. The setup proposed here constitutes an alternative experimental tool to detect Majorana excitations. △ Less

Submitted 8 November, 2014; v1 submitted 2 August, 2014; originally announced August 2014.

Comments: Featured article: cover of the Journal of Applied Physics 116, 17 (2014)

Journal ref: Journal of Applied Physics 116, 17 (2014)