arXiv subjects

Gao Xianlong

Publications and source records attributed to Gao Xianlong.

At least 37 records · Page 2Linked to original sources

arXiv2025

$\mathcal{PT}$-assisted control of Goos-Hänchen shift in cavity magnomechanics

We propose a scheme to manipulate the Goos-Hänchen shift (GHS) of a reflected probe field in a non-Hermitian cavity magnomechanical system. The platform consists of a yttrium-iron-garnet sphere coupled to a microwave cavity, where a strong microwave drive pumps the magnon mode and a weak field probes the cavity. The traveling field's interaction with the magnon induces gain, yielding non-Hermitian dynamics. When the traveling field is oriented at $π/2$ relative to the cavity's $x$-axis, the system realizes $\mathcal{PT}$ symmetry; eigenvalue analysis reveals a third-order exceptional point ($\mathrm{EP}_3$) at a tunable effective magnon-photon coupling. Under balanced gain-loss and finite effective magnomechanical coupling, we demonstrate coherent control of the GHS by steering the system across the $\mathcal{PT}$-symmetric transition and through $\mathrm{EP}_3$ via the effective magnon-photon coupling, enabling pronounced enhancement or suppression of the lateral shift. Furthermore, we show that without effective magnomechanical coupling, the system exhibits a second-order exceptional point ($\mathrm{EP}_2$) with a distinct GHS phase transition. This phase transition vanishes when the effective magnomechanical coupling exceeds a parametric threshold, where strong absorption at resonance suppresses the GHS. We also identify the intracavity length as an additional control parameter for precise shift tuning. Notably, the $\mathcal{PT}$-symmetric configuration yields substantially larger GHS than its Hermitian counterpart. These results advance non-Hermitian magnomechanics and open a route to GHS-based microwave components for quantum switching and precision sensing.

physics.optics↗

arXiv2025

Photonic spin Hall effect in $\mathcal{PT}$-symmetric non-Hermitian cavity magnomechanics

Non-Hermitian cavity magnomechanics (CMM), which incorporates the magnon-photon and magnon-phonon interactions simultaneously, enables rich physical phenomena, including exceptional-point-enhanced sensing, and offers pathways toward topological transitions and nonreciprocal quantum transformation. These interactions exert a pivotal influence on the optical response of a weak probe field and pave the way for novel applications in quantum technologies. In this work, we consider a yttrium-iron-garnet (YIG) sphere coupled to a microwave cavity. The magnon mode of the YIG sphere is directly excited through microwave field coupling, whereas the cavity mode is probed via a weak-field interrogation scheme. The direct interaction of a traveling field with the magnon mode induces gain in the system, thereby establishing non-Hermitian dynamics. The parity-time (PT)-symmetric behavior of a hybrid non-Hermitian CMM is designed and investigated. Eigenvalue spectrum analysis demonstrates that a third-order exceptional point (EP_3) emerges under tunable effective magnon-photon coupling when the traveling field is oriented at an angle of π/2 relative to the cavity's x-axis. The photonic spin Hall effect (PSHE) in a reflected probe field is subsequently examined in such a system. Under balanced gain and loss conditions and in the presence of effective magnon-phonon coupling, tunable effective magnon-photon coupling enables coherent control of the PSHE across the broken PT-symmetric phase, at the EP_3, and in the PT-symmetric phase. Investigation reveals that the PSHE can be significantly enhanced or suppressed via effective magnon-photon coupling. The influence of intracavity length on the PSHE is further explored, providing an additional parameter for fine-tuning the transverse shift. These findings establish a direct correspondence between the PSHE and the underlying non-Hermitian eigenvalue spectrum.

physics.optics↗

arXiv2025

High-Winding-Number Zero-Energy Edge States in Rhombohedral-Stacked Su-Schrieffer-Heeger Multilayers

We study the topological properties of rhombohedral-stacked N-layer Su-Schrieffer-Heeger networks with interlayer coupling. We find that these systems exhibit $2N$-fold degenerate zero-energy edge states with winding number $W=N$, providing a direct route to high-winding-number topological phases where $W$ equals the layer number. Using effective Hamiltonian theory and Zak phase calculations, we demonstrate that the winding number scales linearly with $N$ through a layer-by-layer topological amplification mechanism. We introduce the Wigner entropy as a novel detection method for these edge states, showing that topological boundary states exhibit significantly enhanced Wigner entropy compared to bulk states. Our results establish rhombohedral stacking as a systematic approach for engineering high-winding-number topological insulators with potential applications in quantum information processing.

cond-mat.dis-nn↗

arXiv2025

Anatomy of Non-Hermitian Dynamical Quantum Phase Transitions

We establish a unified framework for dynamical quantum phase transitions (DQPTs) in non-Hermitian systems that encompasses both biorthogonal and self-norm non-biorthogonal formulations for pure and mixed states under quantum quench protocols. Our framework provides explicit expressions for the Loschmidt amplitude, Loschmidt echo, and rate function, revealing a universal geometric signature of DQPTs in the two-band model: orthogonality of two related vectors in two-dimensional real space. Strikingly, we demonstrate that non-biorthogonal quenches from non-Hermitian to Hermitian Hamiltonians under chiral symmetry exhibit emergent topological characteristics of DQPTs, unveiling their fundamental features beyond conventional Hermitian regimes. This work establishes fundamental geometric and topological principles governing quantum criticality in open systems, with implications for quantum sensing and many-body physics in dissipative environments.

quant-ph↗

arXiv2025

Multicomponent cat states with sub-Planckian structures and their optomechanical analogues

We investigate the superposition of coherent states, emphasizing quantum states with distinct Wigner phase-space features relevant to quantum information applications. In this study, we introduce generalized versions of the compass state, which display enhanced phase-space characteristics compared with the conventional compass state, typically a superposition of four coherent states. Our findings reveal that, unlike sub-Planckian structures and phase-space sensitivity of the compass state, these generalized states produce isotropic sub-Planckian structures and sensitivity to phase-space displacements. We demonstrate that these desirable phase-space characteristics are maintained in superpositions comprising at least six distinct coherent states. Furthermore, we show that increasing the number of coherent states in the superposition preserves these characteristics, provided the number remains even. We examine an optomechanical system capable of generating the proposed quantum states, resulting in optomechanical counterparts with nearly identical phase-space structures, thereby suggesting the feasibility of physically realizing these generalized compass states.

quant-ph↗

arXiv2025

Wigner distribution, Wigner entropy, and Anomalous Transport of a Generalized Aubry-André model

We investigate generalized Aubry-André models featuring tunable quasidisordered potentials and a mobility edge that separates extended and localized states, with critical states for the mobility edge confirmed through finite-size scaling analysis. Numerical results demonstrate that extended, critical, and localized states can be distinguished via their phase-space representations, particularly the Wigner distribution. The associated Wigner entropy, derived from this distribution, peaks at the critical state, enabling precise localization of the mobility edge. Additionally, wave-packet dynamics reveal anomalous transport behaviors, including superdiffusion and subdiffusion, bridging ballistic transport and the absence of diffusion.

cond-mat.dis-nn↗

arXiv2025

When Homogeneous Systems Meet Dissipation and Disorder

We investigate the localization and topological properties of the non-equilibrium steady state (NESS) in a one-dimensional homogeneous system. Our results demonstrate that, despite the absence of disorder in the initial system, the NESS can exhibit localization under bond dissipation. These dissipation-driven localization and delocalization phenomena are clearly distinguished using Wigner distributions. Furthermore, we find that the initial localization characteristics of the system significantly influence the localization properties of the NESS. Drawing upon the concept of Bose-Einstein condensate broadening in cold-atom experiments, along with experimental data, we systematically characterize the impact of bond dissipation and disorder on the localization and topological properties of the NESS. The phase diagram reveals that the NESS can be topologically non-trivial even when the initial system is topologically trivial, and that the topological triviality of the initial system strengthens the topological non-triviality of the NESS. This work provides new insights into the localization and topological phase transitions in homogeneous systems induced by bond dissipation and disorder.

cond-mat.dis-nn↗

arXiv2025

Stable supersolids and boselets in spin-orbit-coupled Bose-Einstein condensates with three-body interactions

We explore the stability of supersolid striped waves, plane-wave boselets, and other extended states in one-dimensional spin-orbit-coupled Bose-Einstein condensates with repulsive three-body interactions (R3BIs), modeled by quintic terms in the framework of the corresponding Gross-Pitaevskii equations. In the absence of R3BIs, the extended states are susceptible to the modulational instability (MI) induced by the cubic attractive nonlinearity. Using the linearized Bogoliubov-de-Gennes equations, we identify multiple new types of MI, including baseband, passband, mixedband, and zero-wavenumber-gain ones, which give rise to deterministic rogue waves and complex nonlinear wave patterns. Our analysis reveals that R3BIs eliminate baseband and zero-wavenumber-gain MIs, forming, instead, phonon modes that enable stable boselets. Additionally, mixedband and passband MIs are suppressed, which results in a lattice-like phonon-roton mode that supports a stable supersolid phase. These stable supersolids can be realized using currently available ultracold experimental setup.

cond-mat.quant-gas↗

arXiv2025

Gain-assisted control of the photonic spin Hall effect

In the photonic spin Hall effect (SHE), also known as the transverse shift, incident light photons with opposite spins are spatially separated in the transverse direction due to the spin-orbit interaction of light. Here, we propose a gain-assisted model to control the SHE in the reflected probe light. In this model, a probe light is incident on a cavity containing a three-level dilute gaseous atomic medium, where the interaction between the atom and the control field follows two-photon Raman transitions. We show that the direction of photonic spin accumulations can be switched between positive and negative values across the Brewster angle in both the anomalous and normal dispersion regimes. For the same magnitude of control fields, the peak value of the photonic SHE is higher in the anomalous dispersion region compared to the normal dispersion regime. Additionally, the angular range around the Brewster angle is wider in the normal dispersion regime than in the anomalous dispersion region. Furthermore, the peak value of the photonic SHE and the angular range can be controlled by changing the Rabi frequencies of the control fields and the probe field detuning. The measurement of photonic SHE based on gain assistance may enable spin-related applications such as optical sensing.

physics.atm-clus↗

arXiv2025

Long-range hopping in a quasiperiodic potential weakens the non-Hermitian skin effect

In this paper, we investigate a non-Hermitian Aubry-André-Harper model characterized by power-law hoppings ($1/s^{a}$) and a quasi-periodic parameter $β$, where $a$ denotes the power-law index, $s$ represents the hopping distance, and $β$ belongs to the metallic mean family. In the intermediate phases, we find that ergodic states correspond to complex eigenvalues, multifractal states to real eigenvalues, and localized states may exhibit either complex or real eigenvalues. Moreover, both real and complex energy spectra emerge in the localized phase, with real spectra attributed to pseudo-Hermiticity. Under open boundary conditions, our analysis of fractal dimensions and eigenstates reveals that all ergodic states transform into skin states. Furthermore, we demonstrate that long-range hoppings weaken the skin effect, offering another perspective for exploring non-Hermitian skin effects.

cond-mat.dis-nn↗

arXiv2024

Bound states in one-dimensional systems with colored noise

We investigate the phase transitions in a one-dimensional system with colored noise. Previous studies indicated that the phase diagram of this system included extended and disorder-induced localized phases. However, by studying the properties of wave functions, we find that this phase diagram can be further refined, revealing the existence of a bound phase for the large potential amplitude $W$ and noise control parameter $α$. In the bound phase, the wave function cannot extend throughout the entire chain, tails decay faster than exponentially and its distribution expands as the system size increases. By adjusting the potential amplitude to induce a transition from the extended phase to the bound phase, we find that bound states coexist with extended states in the spectrum. In contrast, when the system transitions from the Anderson localized phase to the bound phase, we do not observe the obvious coexistence of Anderson localized and bound states. Finally, by performing the time evolution, we find that the dynamic transition point of the bound phase is inconsistent with the static one for large $α$.

cond-mat.dis-nn↗

arXiv2024

Enhanced Brewster Angle Shift in Doped Graphene via the Fizeau Drag Effect

We derive the general Fresnel coefficients for reflection by incorporating the Fizeau drag effect in doped graphene, which arises from the unique behavior of its massless Dirac electrons. Using the standard Maxwell equations and constitutive relations, we analyze the influence of this relativistic phenomenon on the optical properties of doped graphene. Our study focuses on the angular shift of Brewster's angle in a structure where monolayer graphene is sandwiched between two static dielectric media. Our findings reveal that the presence of the Fizeau drag effect significantly enhances the Brewster angle shift, leading to substantial modifications in the optical characteristics of the graphene channel, including notable alterations in the reflectance spectrum. We demonstrate that this angular shift can be further amplified by increasing the drift velocities and charge densities of the electrons in graphene, offering a tunable mechanism for controlling optical behavior in graphene-based systems. The findings of this work have significant implications for the design and development of planar photonic devices that take advantage of the optical characteristics of graphene. This breakthrough creates new opportunities for the use of graphene in sophisticated photonic technologies, where exact control over the interactions between light and matter is essential.

cond-mat.mes-hall↗

arXiv2024

Photonic spin Hall effect in Haldane model materials

The photonic spin Hall effect of light beams reflected from the surfaces of various two-dimensional hexagonal crystalline structures, considering their associated time-reversal $\mathcal{T}$ and inversion $\mathcal{I}$ symmetries, is investigated. Employing the Haldane model with tunable parameters as a generic model, we examine the longitudinal and transverse spin-separations of the reflected beam in both topological non-trivial and trivial systems. The study reveals that the sign switching of the PSHE in these materials is attributed to the non-trivial and trivial topology. By manipulating the interplay between spin-orbit coupling and external electric fields, we demonstrate topological phase transitions in buckled Xene monolayer materials through the photonic spin Hall effect. Different behaviors of the photonic spin Hall effect are observed in various topological phases within these materials. Additionally, we explore the reflected spin and valley-polarized spatial shifts in monolayer transition metal dichalcogenides. The photonic spin Hall effect in buckled Xene monolayer materials and transition metal dichalcogenides is highly influenced by the spin and valley degrees of freedom of charge carriers, offering a promising avenue to explore spintronics and valleytronics in these hexagonal materials. We propose that the photonic spin Hall effect in Haldane materials can serve as a metrological tool for optical parameter characterization and as a promising method for determining Chern numbers and topological phase transitions through direct optical weak measurement techniques.

cond-mat.mes-hall↗

arXiv2024

Anomalous correlation-induced dynamical phase transitions

The nonanalyticity of the Loschmidt echo at critical times in quantum quenched systems is termed as the dynamical quantum phase transition, extending the notion of quantum criticality to a nonequilibrium scenario. In this paper, we establish a new paradigm of dynamical phase transitions driven by a sudden change in the internal spatial correlations of the disorder potential in a low-dimensional disordered system. The quench dynamics between prequenched pure and postquenched random system Hamiltonian reveals an anomalous quantum dynamical quantum phase transition triggered by an infinite disorder correlation in the modulation potential. The physical origin of the anomalous phenomenon is associated with the overlap between the two distinctly different extended states. Furthermore, we explore the quench dynamics between the prequenched random and postquenched pure system Hamiltonian. Interestingly, the quenched system undergoes dynamical quantum phase transitions for the prequench white-noise potential in the thermodynamic limit. In addition, the quench dynamics also shows a clear signature of the delocalization phase transition in the correlated Anderson model.

cond-mat.dis-nn↗

arXiv2024

Phase driven unconventional superradiance phase transition in non-Hermitian cascaded quantum Rabi cavities

This study investigates phase-driven symmetry breaking leading to superradiance phase transitions in cascaded non-Hermitian quantum Rabi cavities. Non-Hermiticity is introduced via the phase coupling $φ$ between the atom and the optical field. In the thermodynamic limit of the quantum harmonic oscillator, we analytically derive the superradiance phase boundary, validated by observables. An unconventional quantum phase transition without a Hermitian analogue arises when $|φ|=\fracπ{4}$ or $|φ|=\frac{3π}{4}$, where the phase boundary is uniquely determined by the cavity coupling, at $\mathcal{J}=\frac{1}{2}$, independent of the atom-photon coupling strength $g$. For other $φ$, the phase boundary relies on both $\mathcal{J}$ and $g$, similar to the scenario observed in Hermitian systems. Furthermore, we identify phase-driven first- and second-order superradiance phase transitions, focusing on the quantum criticality of the second-order transition by determining the critical exponents and the universality class. The feasibility of experimental realization is also discussed, aiming to inspire further studies on non-Hermitian superradiance quantum phase transitions.

cond-mat.quant-gas↗

arXiv2024

Compasslike states in a thermal reservoir and fragility of their nonclassical features

Superposed photon-added and photon-subtracted squeezed-vacuum states exhibit sub-Planck phase-space structures and metrological potential similar to the original compass states (superposition of four coherent states), but are more closely tied to modern experiments. Here, we observe that these compasslike states are highly susceptible to loss of quantum coherence when placed in contact with a thermal reservoir; that is, the interaction with the thermal reservoir causes decoherence, which progressively suppresses the capacity of these states to exhibit interference traits. We focus on the sub-Planck structures of these states and find that decoherence effects on these features are stronger with increasing the average thermal photon number of the reservoir, the squeezing parameter, or the quantity of added (or subtracted) photons to the squeezed-vacuum states. Furthermore, we observe that the sub-Planck structures of the photon-subtracted case survive comparatively longer in the thermal reservoir than their counterparts in the photon-added case, and prolonged contact with the thermal reservoir converts these compasslike states into a classical state.

quant-ph↗

arXiv2024

Stable real-energy spectral dynamics with topological transitions and non-Hermitian many-body localization

In this work, the interplay between non-Hermiticity, quasi-disorder, and repulsive interaction is studied for hard-core bosons confined in a one-dimensional optical lattice, where non-Hermiticity is induced by the non-reciprocal hoppings and the on-site gain and loss breaking the time-reversal symmetry. Although the energy spectra of the static system are fully complex, with the evolution of the initial state, the real part of the expectation value of the Hamiltonian under the time-evolved wave function changes stably. By means of the entanglement entropy and its dynamical evolution, as well as the inverse participation ratio, the many-body localization (MBL) is found to play the key role in the stability of the dynamical behavior of the real part of the expectation value, independent of whether the spectrum of the static Hamiltonian is real or complex. In the delocalization phase, the dynamical evolution of the real part of the expectation value is unstable. Meanwhile, the nearest-neighbor level spacings statistics shows the MBL transition accompanied by the transition from the Ginibre distribution to the complex Poisson distribution, different from the one in the time-reversal invariant system. In addition, the dynamical stability of the real part of the energy and the MBL transition can be characterized by the winding number, indicating that the MBL transition and the topological transition occur simultaneously, and the realization of the Hamiltonian is discussed.

cond-mat.dis-nn↗

arXiv2024

Impact of the Fizeau drag effect on Goos-Hänchen shifts in graphene

We investigate the Goos-Hänchen shifts in reflection for a light beam within a graphene structure, utilizing the Fizeau drag effect induced by its massless Dirac electrons in incident light. The magnitudes of spatial and angular shifts for a light beam propagating against the direction of drifting electrons are significantly enhanced, while shifts for a beam co-propagating with the drifting electrons are suppressed. The Goos-Hänchen shifts exhibit augmentation with increasing drift velocities of electrons in graphene. The impact of incident wavelength on the angular and spatial shifts in reflection is discussed. Furthermore, the study highlights the crucial roles of the density of charged particles in graphene, the particle relaxation time, and the thickness of the graphene in manipulating the drag-affected Goos-Hänchen shifts. This investigation offers valuable insights for efficiently guiding light in graphene structures under the influence of the Fizeau drag effect.

cond-mat.mes-hall↗