arXiv subjects

Xiaobing Luo

Publications and source records attributed to Xiaobing Luo.

At least 19 recordsLinked to original sources

arXiv2026

Tunable Statistics-Induced Caging in the Anyon-Hubbard Model

We study the quantum dynamics of two interacting anyons in the Anyon-Hubbard model on a four-site plaquette, a system that is exactly mappable to a Bose-Hubbard model. We reveal that static Aharonov-Bohm (AB) caging, induced by only specific statistical phases, emerges in the strongly interacting limit but breaks down under weak interparticle interactions. To address this, we demonstrate that statistical-factor-induced AB caging can be dynamically restored via Floquet engineering. This dynamical mechanism, governed by the synthetic Floquet flux and the anyonic statistical phase, extends the caging effect into the weakly interacting regime across the full spectrum of statistical phases. Furthermore, we show that the external drive enables the selective caging of anyons, providing an efficient approach for manipulating anyons and identifying statistical phases.

quant-ph↗

arXiv2026

Chiral Quantum Transport with Perfect Circulation: From Floquet Engineering toAnyonic Dynamics

Perfect chiral circulation-the sequential transfer of a quantum state around a closed loop with unit fidelity-has been achieved in specific few-site systems, yet the universal physical conditions underlying this phenomenon remain unclear. We prove that discrete translational invariance and an equidistant energy spectrum together constitute the necessary and sufficient conditions for perfect chiral circulation. With this criterion established, an exact closed-form Hamiltonian valid for arbitrary $N$-site rings naturally follows. In the minimal three-site ring, we demonstrate two physically distinct realizations: Floquet engineering of a driven open chain that restores translational invariance by equalizing the couplings, and correlated doublon dynamics in an anyon-Hubbard model where fractional statistics intrinsically provide the chiral flux that renders the spectrum equidistant. Our results establish unified physical criteria for perfect chiral circulation and demonstrate their applicability across diverse platforms such as superconducting circuits, cold atoms, classical electrical circuits, and photonic synthetic dimensions.

quant-ph↗

arXiv2025

Magnetic flux induced higher-order topological superconductivity

Higher-order topological superconductivity typically depends on spin-orbit interaction, and often necessitates well designed sample structures, nodal superconducting pairings or complex magnetic order. In this work, we propose a model that incorporates a Zeeman field, antiferromagnetic order, and $s$-wave superconducting pairing, all without the need for spin-orbit interaction. In a two-dimensional system, we realize a second-order topological superconductor by utilizing a staggered flux, provided that the Zeeman field is oriented perpendicular to the magnetic order moments. In three-dimensional systems, we achieve second- and third-order topological superconductors in theory, through stacking the two-dimensional second-order topological superconductor.

cond-mat.mes-hall↗

arXiv2025

Controlling the $\mathcal{PT}$ Symmetry Breaking Threshold in Bipartite Lattice Systems with Floquet Topological Edge States

We investigate the control of the parity-time ($\mathcal{PT}$)-symmetry breaking threshold in a periodically driven one-dimensional dimerized lattice with spatially symmetric gain and loss defects. We elucidate the contrasting roles played by Floquet topological edge states in determining the $\mathcal{PT}$ symmetry breaking threshold within the high- and low-frequency driving regimes. In the high-frequency regime, the participation of topological edge states in $\mathcal{PT}$ symmetry breaking is contingent upon the position of the $\mathcal{PT}$-symmetric defect pairs, whereas in the low-frequency regime, their participation is unconditional and independent of the defect pairs placement, resulting in a universal zero threshold. We establish a direct link between the symmetry-breaking threshold and how the spatial profile of the Floquet topological edge states evolves over one driving period. We further demonstrate that lattices with an odd number of sites exhibit unique threshold patterns, in contrast to even-sized systems. Moreover, applying co-frequency periodic driving to the defect pairs, which preserves time-reversal symmetry, can significantly enhance the $\mathcal{PT}$ symmetry-breaking threshold.

quant-ph↗

arXiv2025

Generation and Stabilization of Bound States in the Continuum in Dissipative Floquet Optical Lattices

This paper investigates the generation and stabilization of bound states in the continuum (BICs) in a one-dimensional dissipative Floquet lattice. We find a different mechanism for the generation of stable BICs in the open one-dimensional lattice system, which stems from a peculiar dark Floquet state, a state with zero quasi-energy and negligible population on the lossy sites. Our results reveal that the evolutionary stability of BICs resulting from the dark Floquet state can be significantly enhanced, as evidenced by their very low decay rate, by increasing the driving frequency or, counterintuitively, increasing the dissipation strength. We further demonstrate that stable dark Floquet BICs can robustly persist even in nonlinear regimes. The existence of these stable dark Floquet BICs can be attributed to the role of higher-order correction terms in the effective Floquet Hamiltonian derived via the high-frequency expansion (HFE) method. Furthermore, we demonstrate that incorporating non-Hermitian dissipation can extend the parameter regime for the existence of BICs, and the dissipation-induced BICs can lead to complete reflection of wave packets. Our findings provide theoretical support for the experimental realization of stable BICs in dissipative quantum systems.

quant-ph↗

arXiv2024

Quantum-classical correspondence of non-Hermitian spin-orbit coupled bosonic junction

We investigate the classical-quantum correspondence of non-Hermitian Spin-orbit (SO)-coupled bosonic junctions, where an effective decay term is introduced in one of the two wells. Starting from the normalized two-point functions, we analytically demonstrate that the mean-field system has a classical Hamiltonian structure, and we successfully derive a non-Hermitian discrete nonlinear Schrödinger (Gross-Pitaevskii) equation. We discover that near the symmetry-breaking phase transition point, the correspondence between classical (mean-field) and quantum dynamics is more likely to break down. When the effective spin-orbit coupling (SOC) strength assumes half-integer values, atomic self-trapping in the non-lossy well definitely occurs, regardless of the system parameters, and the quantum dynamics is insensitive to the number of particles. Additionally, we reveal that in both the mean-field and many-particle models, the SOC effects can greatly promote the synchronous periodic oscillations between the spin-up and spin-down components, and this synchronization dynamics is protected by a symmetry mechanism.

quant-ph↗

arXiv2024

Spin-orbit coupling mediated photon-like resonance for a single atom trapped in a symmetric double well

We employ a method involving coherent periodic modulation of Raman laser intensity to induce resonance transitions between energy levels of a spin-orbit coupled atom in a symmetric double-well trap. By integrating photon-assisted tunneling (PAT) technique with spin-orbit coupling (SOC), we achieve resonance transitions between the predefined energy levels of the atom, thereby enabling further precise control of the atom's dynamics. We observe that such photon-like resonance can induce a transition from a localized state to atomic Rabi oscillation between two wells, or effectively reduce tunneling as manifested by a quantum beating phenomenon. Moreover, such resonance transitions have the potential to induce spin flipping in a spin-orbit coupled atom. Additionally, the SOC-mediated transition from multiphoton resonance to fundamental resonance and the SOC-induced resonance suppression are also discovered. In these cases, the analytical results of the effective coupling coefficients of the resonance transition derived from a four-level model can account for the entire dynamics, demonstrating surprisingly good agreement with the numerically exact results based on the realistic continuous model.

quant-ph↗

arXiv2024

Photon-assisted tunneling resonantly controlling spin current of a spin-orbit-coupled atom in a toroidal trap

The periodic flashing potential has proven to be a powerful tool for investigating directed atomic currents. By applying the flashing ring-shaped potential to spin-orbit (SO) coupled, noninteracting Bose-Einstein condensate (BEC) systems, through photon-assisted tunneling (resonance) techniques, we demonstrate the generation of tunable alternating (AC) spin and atomic mass currents that can be precisely controlled in terms of direction and strength. The underlying mechanism behind this phenomenon is that the flashing potential supplies enough photons to induce Rabi oscillations and provides momentum transfer for spin and atomic transport. As the single-particle ground state of the unperturbed SO-coupled BEC depends on the Raman coupling strength, we demonstrate how to generate and control AC spin currents in the cases where the initial state resides in a single-well or double-well phase. In particular, we realize and explain the mechanism of generating a net AC spin current without mass current through single-photon resonance processes. It is shown that these interesting resonance phenomena can be analytically described only by the simple three-level model, which creates the possibility of transparent controls of spin dynamics.

cond-mat.quant-gas↗

arXiv2024

Magnetic flux induced topological superconductivity in magnetic atomic rings

There have been numerous studies on topological superconductivity in magnetic atomic chains deposited on s-wave superconductors. Most of these investigations have focused on spin-orbit interactions or helical spin orders. In this paper, we propose a model for achieving one-dimensional topological superconductivity in a magnetic atomic ring. This model utilizes a magnetic field and an antiferromagnetic/ferromagnetic order, under the condition that the magnetic field is perpendicular to the moments of the magnetic order. On a quasi-one-dimensional substrate surface, where the half-filled ring favors an antiferromagnetic configuration, we demonstrate that either the magnetic field itself or a Rashba spin-orbit coupling guarantees the perpendicularity. On a two-dimensional surface, where the ring favors ferromagnetic orders, the perpendicularity is achieved by introducing a minor Rashba spin-orbit coupling.

cond-mat.mes-hall↗

arXiv2024

Controlled pumping of matter-wave solitons in a one-dimensional optical superlattice

We study the pumping of matter-wave solitons formed in Bose-Einstein condensates (BECs) with attractive atomic interactions that are loaded into optical superlattices in which one of the lattices is moving with respect to the other. We find that solitons exhibit the remarkably similar pumping properties in both shallow and deep lattices, and that for exactly the same soliton initially excited, switching between integer (fractional) pumping and trapping can be achieved by simply adjusting the lattice parameters. In addition, we find that the gap solitons, which bifurcate from the lowest energy band in a semi-infinite band gap, also exhibit this lattice-parameter-dependent pumping and trapping. The treatment of solitons as classical particles with effective centre-of-mass equations of motion provides a good description of this parameter-dependent integer (fractional) pumping and trapping of solitons.

quant-ph↗

arXiv2023

Surface superconductor-insulator transition: Reduction of the critical electric field by Hartree-Fock potential

Recently, a surface superconductor-insulator transition has been predicted for a bulk superconductor in an electric field applied perpendicular to its surface. The related calculations were performed within a one-dimensional Hubbard model by numerically solving the Bogoliubov-de Gennes (BdG) equations without the Hartree-Fock (HF) interaction potential. The phase diagram of the surface superconducting, metallic, and insulating states was obtained as dependent on the electric field and temperature. This diagram was found to be in agreement with experimental results reported previously for (Li,Fe)OHFeSe thin flakes. In the present work, by taking into account the HF potential, we find that the latter acts as a kind of an extra electrostatic potential that enhances the electric-field effects on the surface states. The qualitative features of the phase diagram remain the same but the surface superconductor-insulator transition occurs at significantly lower electric fields, which supports prospects of its experimental observation in bulk samples.

cond-mat.supr-con↗

arXiv2023

Chaos signatures of current phase transition in a toroidal trap

In this work we demonstrate how the directed motion of atomic Bose-Einstein condensates in a toroidal trap can be controlled by applying a zero-mean oscillatory driving field. We show that due to the self-trapping effect in momentum space, the oscillatory amplitude of the current can be significantly suppressed and a nearly constant directed current can be obtained preserving the initial current values, by decreasing the driving amplitude, even when the atomic interactions are relatively small. We also reveal numerically the mean-field chaos can serve as an indicator of a quantum phase transition between the vanishing current regime and nonvanishing current regime. Our results are corroborated by an effective three-mode model, which provides an excellent account of the ratchet dynamics of the system.

quant-ph↗

arXiv2023

Tailoring of the interference-induced surface superconductivity by an applied electric field

Nucleation of the pair condensate near surfaces above the upper critical magnetic field and the pair-condensate enhancement/suppression induced by changes in the electron-phonon interaction at interfaces are the most known examples of the surface superconductivity. Recently, another example has been reported, when the surface enhancement of the critical superconducting temperature occurs due to quantum interference. In this case the pair states spread over the entire volume of the system while exhibiting the constructive interference near the surface. In the present work we investigate how an applied electric field impacts the interference-induced surface superconductivity. The study is based on a numerical solution of the self-consistent Bogoliubov-de Gennes equations for a one-dimensional attractive Hubbard model. Our results demonstrate that the surface superconducting characteristics, especially the surface critical temperature, are sensitive to the applied electric field and can be tailored by changing its magnitude.

cond-mat.supr-con↗

arXiv2023

Ratchet current in a $\mathcal{PT}$-symmetric Floquet quantum system with symmetric sinusoidal driving

We consider the ratchet dynamics in a $\mathcal{PT}$-symmetric Floquet quantum system with symmetric temporal (harmonic) driving. In the exact $\mathcal{PT}$ phase, for a finite number of resonant frequencies, we show that the long-lasting resonant currents can be generated with the symmetric time-continuous driving, which would otherwise forbid the generation of directed currents in the Hermitian limit. Such a non-Hermitian resonant current can be enhanced by increasing the non-Hermitian level, and in particular, the resonant current peaks (reaches the largest negative value) under the condition that the imaginary part of the potential depth is equal to the real part, at which the stable asymptotic current occurs owing to exceptional points (EPs) mechanism. Moreover, the directed currents originating from the symmetry breaking are reported, which increase linearly with the driving frequency, the mechanism behind which is that the cutoff of the momentum eigenstates for the Floquet state with maximum imaginary quasienergy increases as the driving frequency is continuously increased. We also present a non-Hermitian three-level model that can account for the resonant currents and gives surprisingly good agreement with direct numerical results for weak driving, even in the $\mathcal{PT}$-broken regime for the first-order resonance. Our results provide a new means of realizing the non-Hermiticity-controlled ratchet current by means of a smooth continuous driving, previously used only to generate currents in Hermitian systems.

quant-ph↗

arXiv2023

Scattering of one-dimensional quantum droplets by a reflectionless potential well

We investigate, both analytically and numerically, the scattering of one-dimensional quantum droplets by a Pöschl-Teller reflectionless potential well, confirming that there is a sharp transition between full reflection and full transmission at a certain critical incident speed for both small droplets and large flat-top droplets. We observe sharp differences between small quantum droplet scattering and large quantum droplet scattering. The scattering of small quantum droplets is similar to that of solitons, where a spatially symmetric trapped mode is formed at the critical speed, whereas for large quantum droplets a spatially asymmetric trapped mode is formed. Additionally, a nonmonotonous dependence of the critical speed on the atom number is identified$:$ on the small-droplet side, the critical speed increases with the atom number, while in the flat-top regime, the critical speed decreases with increasing the atom number. Strikingly, the scattering excites internal modes below the particle-emission threshold, preventing the quantum droplets from emitting radiation upon interaction with the potential. Analysis of the small-amplitude excitation spectrum shows that as the number of particles increases, it becomes increasingly difficult to emit particles outside the droplet during scattering, while radiation from solitons cannot be completely avoided. Finally, we study the collision of two quantum droplets at the reflectionless potential, revealing the role of the $π$-phase difference ``generator'' played by the reflectionless potential.

quant-ph↗

arXiv2023

Interference-induced surface superconductivity:Enhancement by tuning the Debye energy

In the usual perception, surface superconductivity is associated with the surface nucleation of a superconducting condensate above the upper critical field in type-II superconductors or with a rearrangement of phonon properties and the electron-phonon coupling near surfaces/interfaces. Recently, it has been found that there is another example when the surface superconducting temperature is increased up to 20-25% as compared to the bulk one due to constructive interference of superconducting pair states. In the present work, we demonstrate that in fact, such an interferenceinduced enhancement can be much more pronounced, up to nearly 70%. Furthermore, here it is shown that such an interference enhancement persists over a wide range of microscopic parameters.

cond-mat.supr-con↗

arXiv2022

Spin Josephson effects of spin-orbit-coupled Bose-Einstein condensates in a non-Hermitian double well

In this paper, we investigate the spin and tunneling dynamics of a spin-orbit-coupled noninteracting Bose-Einstein condensate in a periodically driven non-Hermitian double-well potential. Under high-frequency driving, we obtain the effective time-averaged Hamiltonian by using the standard time-averaging method, and analytically calculate the Floquet quasienergies, revealing that the parity-time (PT)-breaking phase transition appears even for arbitrarily small non-Hermitian parameters when the spin-orbit coupling strength takes half-integer value, irrespective of the values of other parameters used. When the system is PT-symmetric with balanced gain and loss, we find numerically and analytically that in the broken PT-symmetric regions, there will exist the net spin current together with a vanishing atomic current, if we drop the contribution of the exponential growth of the norm to the current behaviors. When the system is non-PT-symmetric, though the quasienergies are partial complex, a stable net spin current can be generated by controlling the periodic driving field, which is accompanied by a spatial localization of the condensate in the well with gain. The results deepen the understanding of non-Hermitian physics and could be useful for engineering a variety of devices for spintronics.

cond-mat.quant-gas↗

arXiv2022

Analytical results for the superflow of spin-orbit-coupled Bose-Einstein condensates in optical lattices

In this paper, we show that for sufficiently strong atomic interactions, there exist analytical solutions of current-carrying nonlinear Bloch states at the Brillouin zone edge to the model of spin-orbit-coupled Bose-Einstein condensates (BECs) with symmetric spin interaction loaded into optical lattices. These simple but generic exact solutions provide an analytical demonstration of some intriguing properties which have neither an analog in the regular BEC lattice systems nor in the uniform spin-orbit-coupled BEC systems. It is an analytical example for understanding the superfluid and other related properties of the spin-orbit-coupled BEC lattice systems.

cond-mat.quant-gas↗