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Driven square lattice of quantum dots in a magnetic field coupled to a cylindrical FIR-photon cavity
Authors:
Vidar Gudmundsson,
Vram Mughnetsyan,
Hsi-Sheng Goan,
Jeng-Da Chai,
Nzar Rauf Abdullah,
Chi-Shung Tang,
Wen-Hsuan Kuan,
Valeriu Moldoveanu,
Andrei Manolescu
Abstract:
We present a comprehensive computational study of driven quantum dot arrays in a square lattice configuration, subject to an external magnetic field and coupled to a cylindrical far-infrared photon cavity. The driving is introduced through a harmonic modulation of the full electron-photon interaction, therefore including both paramagnetic and diamagnetic contributions. The electron-electron Coulom…
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We present a comprehensive computational study of driven quantum dot arrays in a square lattice configuration, subject to an external magnetic field and coupled to a cylindrical far-infrared photon cavity. The driving is introduced through a harmonic modulation of the full electron-photon interaction, therefore including both paramagnetic and diamagnetic contributions. The electron-electron Coulomb interactions are treated within density functional theory, while the electron-photon coupling is modeled using a many-body configuration interaction approach at each iteration of the density functional. By exploiting the unique properties of the cylindrical TE$_{011}$ cavity mode, we demonstrate selective enhancement of diamagnetic two-photon transitions. Our results reveal that the effectiveness of harmonic modulation of the electron-photon interaction is strongly dependent on both the driving frequency and the electron occupation number per dot. When the driving frequency approaches twice the cavity photon frequency, the system exhibits resonant behavior characterized by efficient photon pumping, occupation of higher-order photon replicas, and activation of collective radial Coulomb breathing modes. These findings establish a controllable mechanism for manipulating photon states in coupled quantum dot-cavity systems and provide insights into the interplay among harmonic modulation, photonic excitations, magnetic confinement, and many-body electron correlations in dimensionally reduced nanostructures.
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Submitted 7 July, 2026;
originally announced July 2026.
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Signatures of broken symmetries in the excitations of a periodic 2DEG coupled to a cylindrical photon cavity
Authors:
Vidar Gudmundsson,
Vram Mughnetsyan,
Hsi-Sheng Goan,
Jeng-Da Chai,
Nzar Rauf Abdullah,
Chi-Shung Tang,
Wen-Hsuan Kuan,
Valeriu Moldoveanu,
Andrei Manolescu
Abstract:
In a two-dimensional electron gas (2DEG) in a periodic lateral superlattice subjected to an external homogeneous magnetic field and in a cylindrical far-infrared photon cavity we search for effects of broken symmetries: Static ones, stemming from the unit cell of the system, and the external magnetic field together with the dynamic ones caused by the vector potential of the cavity promoting magnet…
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In a two-dimensional electron gas (2DEG) in a periodic lateral superlattice subjected to an external homogeneous magnetic field and in a cylindrical far-infrared photon cavity we search for effects of broken symmetries: Static ones, stemming from the unit cell of the system, and the external magnetic field together with the dynamic ones caused by the vector potential of the cavity promoting magnetic types of transitions, and the chirality of the excitation pulse. The Coulomb interaction of the electrons is described within density functional theory, but the electron-photon interactions are handled by a configuration interaction formalism within each step of the density functional approach, both for the static and the dynamic system. In the dynamical calculations we observe weak chiral effects that change character as the strength of the electron-photon interaction and the external magnetic field are increased. From the analysis of the chiral effects we identify an important connection of the para- and diamagnetic electron-photon interactions that promotes the diamagnetic interaction in the present system when the interaction strength is increased. Furthermore, the asymmetric potential in the unit cell of the square array activates collective oscillation modes that are not present in the system when the unit cell has a higher symmetry.
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Submitted 8 October, 2025;
originally announced October 2025.
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Suppression of Bloch Oscillations and Nonreciprocal Landau-Zener Tunneling in Bose-Einstein Quantum Droplets
Authors:
Szu-Cheng Cheng,
Yu-Wen Wang,
Wen-Feng Hsieh,
Vidar Gudmundsson,
Wen-Hsuan Kuan
Abstract:
We investigate the nonlinear Bloch dynamics and Landau-Zener (LZ) tunneling of quantum droplets in optical lattices. We show that the Lee-Huang-Yang (LHY) correction not only stabilizes the self-bound droplet, but also introduces nonlinear phase feedback that competes with the lattice-induced coherent motion. In the deep-lattice regime, applying a generalized super-Gaussian ansatz within the tight…
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We investigate the nonlinear Bloch dynamics and Landau-Zener (LZ) tunneling of quantum droplets in optical lattices. We show that the Lee-Huang-Yang (LHY) correction not only stabilizes the self-bound droplet, but also introduces nonlinear phase feedback that competes with the lattice-induced coherent motion. In the deep-lattice regime, applying a generalized super-Gaussian ansatz within the tight-binding model demonstrates that chirp accumulation modifies the internal phase profile and renormalizes mobility. The coherent Bloch oscillations (BO) are progressively arrested in the presence of the LHY interaction without dissipative damping. In the shallow-lattice regime, the system is mapped onto a nonlinear two-level Josephson-analog model in which the mean-field and LHY contributions enter through an effective nonlinear detuning, deforming the adiabatic spectrum and generating looped bands. Using the classical action-angle formulation, we demonstrate that the nonlinear LZ tunneling is governed by the underlying phase-space structure. In particular, the LHY correction suppresses the tunneling probability by modifying the separatrix action and renormalizing the exponential sweep-rate scaling through a nonlinear weighting factor. We further identify pronounced nonreciprocal LZ tunneling arising from branch-dependent population imbalance and the nonlinearly induced inertia. These results establish a unified mechanism in which the LHY interaction suppresses both coherent Bloch dynamics and interband tunneling by reorganizing the dynamical exchange among lattice motion, population imbalance, and internal phase modulation.
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Submitted 2 July, 2026; v1 submitted 4 August, 2025;
originally announced August 2025.
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Dynamics of Rapidly Rotating Bose-Einstein Quantum Droplets
Authors:
Szu-Cheng Cheng,
Yu-Wen Wang,
Wen-Hsuan Kuan
Abstract:
This work theoretically investigates \textcolor{black}{the stationary properties} and the dynamics of the rotating quantum liquid droplets confined in a two-dimensional symmetric anharmonic trap. Mimicking the quantum Hall systems, the modified Gross-Pitaevskii equation with the inclusion of the Lee-Huang-Yang nonlinear interaction is analytically solved, and the role of the Landau-level mixing ef…
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This work theoretically investigates \textcolor{black}{the stationary properties} and the dynamics of the rotating quantum liquid droplets confined in a two-dimensional symmetric anharmonic trap. Mimicking the quantum Hall systems, the modified Gross-Pitaevskii equation with the inclusion of the Lee-Huang-Yang nonlinear interaction is analytically solved, and the role of the Landau-level mixing effect is addressed. \textcolor{black}{Via controlling the nonlinear interaction and the rotation speed, the rotating quantum droplet with multiply quantized vortex can be created, and the preference of the energetically favored quantum states can be distinguished in the phase diagram. To better interpret the underlying physics of the phase singularities, a brief comparison of the rotating quantum droplet and the optical vortex is made. The investigation of the long-term evolution of the rotating quantum droplets confirms the stability of the quantum states. At certain rotation speeds, the multi-periodic trajectories and breathings provide evidence of the emergence of the collective excitation of the surface mode in the vortex state. For quantum droplets carrying multiply quantized vortex, the microscopic snapshots of the rotation field adjusted current density distribution show that the combined nonlinear interaction and the anharmonic trapping potential can provide the restoring force to lead the quantum droplet to a regular and stable revolution and reach the dynamic equilibrium, revealing the signature of the generation of superfluids in the new kind of low-dimensional quantum liquids.
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Submitted 4 June, 2024; v1 submitted 15 February, 2023;
originally announced February 2023.
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Magneto-Optical Quantum Switching in a System of Spinor Excitons
Authors:
Wen-Hsuan Kuan,
Vidar Gudmundsson
Abstract:
In this work we investigate magneto-optical properties of two-dimensional semiconductor quantum-ring excitons with Rashba and Dresselhaus spin-orbit interactions threaded by a magnetic flux perpendicular to the plane of the ring. By calculating the excitonic Aharonov-Bohm spectrum, we study the Coulomb and spin-orbit effects on the Aharonov-Bohm features. From the light-matter interactions of the…
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In this work we investigate magneto-optical properties of two-dimensional semiconductor quantum-ring excitons with Rashba and Dresselhaus spin-orbit interactions threaded by a magnetic flux perpendicular to the plane of the ring. By calculating the excitonic Aharonov-Bohm spectrum, we study the Coulomb and spin-orbit effects on the Aharonov-Bohm features. From the light-matter interactions of the excitons, we find that for scalar excitons, there are open channels for spontaneous recombination resulting in a bright photoluminescence spectrum, whereas the forbidden recombination of dipolar excitons results in a dark photoluminescence spectrum. We investigate the generation of persistent charge and spin currents. The exploration of spin orientations manifests that by adjusting the strength of the spin-orbit interactions, the exciton can be constructed as a squeezed complex with specific spin polarization. Moreover, a coherently moving dipolar exciton acquires a nontrivial dual Aharonov-Casher phase, creating the possibility to generate persistent dipole currents and spin dipole currents. Our study reveals that a manipulation of the spin-orbit interactions provides a potential application for quantum-ring spinor excitons to be utilized in nano-scaled magneto-optical switches.
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Submitted 25 May, 2017;
originally announced May 2017.
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Spectral properties and magneto-optical excitations in semiconductor double-rings under Rashba spin-orbit interaction
Authors:
Wen-Hsuan Kuan,
Chi-Shung Tang,
Cheng-Hung Chang
Abstract:
We have numerically solved the Hamiltonian of an electron in a semiconductor double ring subjected to the magnetic flux and Rashba spin-orbit interaction. It is found that the Aharonov-Bohm energy spectrum reveals multi-zigzag periodic structures. The investigations of spin-dependent electron dynamics via Rabi oscillations in two-level and three-level systems demonstrate the possibility of manip…
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We have numerically solved the Hamiltonian of an electron in a semiconductor double ring subjected to the magnetic flux and Rashba spin-orbit interaction. It is found that the Aharonov-Bohm energy spectrum reveals multi-zigzag periodic structures. The investigations of spin-dependent electron dynamics via Rabi oscillations in two-level and three-level systems demonstrate the possibility of manipulating quantum states. Our results show that the optimal control of photon-assisted inter-ring transitions can be achieved by employing cascade-type and $Λ$-type transition mechanisms. Under chirped pulse impulsions, a robust and complete transfer of an electron to the final state is shown to coincide with the estimation of the Landau-Zener formula.
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Submitted 24 March, 2007;
originally announced March 2007.
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Energy levels of a parabolically confined quantum dot in the presence of spin-orbit interaction
Authors:
W. H. Kuan,
C. S. Tang,
W. Xu
Abstract:
We present a theoretical study of the energy levels in a parabolically confined quantum dot in the presence of the Rashba spin-orbit interaction (SOI). The features of some low-lying states in various strengths of the SOI are examined at finite magnetic fields. The presence of a magnetic field enhances the possibility of the spin polarization and the SOI leads to different energy dependence on m…
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We present a theoretical study of the energy levels in a parabolically confined quantum dot in the presence of the Rashba spin-orbit interaction (SOI). The features of some low-lying states in various strengths of the SOI are examined at finite magnetic fields. The presence of a magnetic field enhances the possibility of the spin polarization and the SOI leads to different energy dependence on magnetic fields applied. Furthermore, in high magnetic fields, the spectra of low-lying states show basic features of Fock-Darwin levels as well as Landau levels.
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Submitted 12 March, 2004; v1 submitted 3 March, 2004;
originally announced March 2004.