arXiv subjects

Junhui Cao

Publications and source records attributed to Junhui Cao.

9 recordsLinked to original sources

arXiv2026

Three-Dimensional Kardar--Parisi--Zhang Scaling in Polariton Condensates

Kardar--Parisi--Zhang (KPZ) universality provides an example of macroscopic scaling generated by microscopic violation of detailed balance. While one- and two-dimensional realizations have been explored in driven condensates and growing interfaces, demonstrating KPZ scaling in three spatial dimensions remains a major challenge. Here we propose a three-dimensional exciton-polariton crystal as a platform for observation of 3D KPZ universality. Starting from a stochastic driven-dissipative Gross-Pitaevskii equation for a condensate formed in a three-dimensional photonic-crystal lower-polariton band, we eliminate the massive density and reservoir modes and obtain an effective $3+1$-dimensional KPZ equation for the condensate phase. Numerical simulations of both the KPZ equation and the full driven-dissipative polariton model show an intermediate-asymptotic regime in which the first-order coherence obeys $-\ln |\gone(0,\Delta t)|\propto |\Delta t|^{2\beta}$ and $-\ln |\gone(\Delta r,0)|\propto |\Delta r|^{2\chi}$, with exponents consistent with the $3+1$ KPZ benchmarks $\beta= 0.1845$, $\chi= 0.3135$. Our results identify three-dimensional polariton crystals as a controllable quantum fluid route to higher-dimensional nonequilibrium universality.

cond-mat.stat-mech↗

arXiv2026

Exceptional Cones from an Indefinite Bogoliubov Metric in Hyperbolic Polariton Condensates

Long-wavelength Bogoliubov phonons in an ordinary condensate realize the standard acoustic Lorentz metric. We show that a condensate formed in a hyperbolic polariton band realizes a different collective geometry with an indefinite Bogoliubov metric whose spatial signature is inherited from the opposite signs of the band curvatures. This metric converts the acoustic light cone into a hyperbolic stability wedge, separating propagating quasiparticles from dynamically unstable ones. In a driven-dissipative condensate, gain saturation turns this metric relation into a non-Hermitian Bogoliubov dispersion. The zero-discriminant surface becomes an exceptional cone in the parametric space $(q_x,q_y,\Delta_{\rm NH})$, appearing as an exceptional hyperbola at fixed gain saturation. Across this surface the Bogoliubov branches coalesce, the biorthogonal phase rigidity collapses, and the spectrum changes from propagation to amplified or overdamped dynamics. Our results identify hyperbolic polariton condensates as a controllable setting where non-Hermitian exceptional degeneracies are organized by an effective Bogoliubov metric.

cond-mat.mes-hall↗

arXiv2026

Bose-Einstein Condensation of Three-Dimensional Exciton-Polaritons

We develop a band-structure-based theory of exciton-polaritons in a three-dimensional inverse-opal photonic crystal doped with semiconductor quantum dots. Starting from a symmetry-selected bright photonic branch near the photonic gap edge, we construct an exciton-photon Hamiltonian and obtain a lower-polariton band with a W-point global minimum and a nearby X-point van-Hove-enhanced density of states. We show that the W valleys determine the equilibrium Bose-Einstein condensation threshold, while the X-point saddle provides a finite excited-state capacity that renormalizes the critical temperature when the W-X offset is thermally accessible. By tuning the exciton resonance and the light-matter coupling, the relative W-X ordering can be reconstructed, leading to a strong variation of the critical temperature. We further formulate a momentum-resolved Boltzmann model for driven-dissipative kinetics. Under non-resonant pumping, reservoir feeding, radiative decay, and inter-sector relaxation can produce either W-dominated condensation, a mixed W-X regime, or an X-dominated nonequilibrium coherent state. Our results establish three-dimensional photonic-crystal polaritons as a platform where condensation is controlled not only by the band minimum but also by valley geometry, van-Hove-enhanced phase space, and relaxation pathways.

cond-mat.mes-hall↗

arXiv2026

Emergent Magnetic Monopole in Artificial Polariton Spin Ice

Artificial spin ice provides a versatile setting for emergent gauge fields and magnetic monopole excitations. Here we propose a driven-dissipative polariton realization of artificial spin ice, in which the circular polarization of each link mode plays the role of an Ising degree of freedom, while an auxiliary lossy vertex mode dynamically enforces a local ice-rule constraint. Adiabatic elimination of the vertex mode yields an effective spin-ice penalty, favoring the two-in two-out manifold in the steady state. We show that local polarization flips generate monopole-antimonopole defects, and that sequential flips transport these defects across the lattice while defining a Dirac string. In an extended spin-ice geometry, the vertex charges and their dynamics can be directly reconstructed from polarization-resolved real-space imaging. Our results establish polariton lattices as a controllable photonic platform for creating, manipulating, and observing emergent gauge charges in nonequilibrium spin-ice systems.

cond-mat.mes-hall↗

arXiv2026

Collective Nuclear Polaritons with Coherent and Tunable Excitation Dynamics

We propose collective nuclear polaritons formed by hybridizing a 229Th nuclear ensemble with a vacuum-ultraviolet cavity mode generated via four-wave mixing, achieving a collective light-matter coupling that scales as $\sqrt{N}$. In the strong-coupling regime the system displays vacuum Rabi oscillations, indicating the hybridization between cavity photons and nuclear excitations. In the superradiant regime, the stored excitation is released in a cooperative burst with peak intensity scaling as $N^2$. The emission lifetime shrinks from thousands of seconds to the millisecond scale and remains tunable. Detuning sweeps across the polariton avoided crossing allow adiabatic conversion of the photonic excitation into a collective nuclear excitation, enabling reversible quantum storage. Our results demonstrate that cavity-mediated nuclear polaritons enable deterministic lifetime engineering and coherent quantum storage in nuclear systems.

quant-ph↗

arXiv2025

Acoustic Black Holes in a Shock-Wave Exciton-Polariton Condensate

We demonstrate the spontaneous formation of acoustic black holes in exciton-polariton condensates triggered by discontinuous Riemann-type initial conditions. Starting from a quasi-conservative Gross-Pitaevskii model, we show that nonlinear dispersive shock waves naturally generate spatial regions where the local flow velocity exceeds the speed of sound, creating a self-induced transonic interface that functions as an acoustic horizon. Unlike previous schemes relying on externally engineered potentials or pump-loss landscapes, our approach reveals that the intrinsic nonlinear hydrodynamics of polariton fluids alone can lead to horizon formation. Using Whitham modulation theory and numerical simulations, we characterize the transition between subsonic and supersonic regimes and estimate the corresponding surface gravity and Hawking temperature. This mechanism opens a new route toward realizing polariton black holes and studying analogue gravitational effects, including Hawking-like emission, in Bose-Einstein quantum liquids.

cond-mat.mes-hall↗

arXiv2025

Polariton XY-simulators revisited

Arrays of bosonic condensates of exciton-polaritons have emerged as a promising platform for simulating classical XY models, capable of rapidly reaching phase-locked states that may be mapped to arrays of two-dimensional classical spins. However, it remains unclear whether these states genuinely minimize the corresponding XY Hamiltonian and how the convergence time scales with the system size. Here, we develop an analytical model revealing that an array of $N$ condensates possesses $N$ stable phase configurations. The system selectively amplifies a specific configuration dependent on the pump power: at low power, the state with the smallest eigenvalue of an effective XY Hamiltonian is favored, while at high power, the state with the largest eigenvalue prevails. At intermediate pump powers, the system visits all eigenstates of the Hamiltonian. Crucially, the formation rate for any of these phase-locked states remains on the order of 100 ps, independent of the size of the array, demonstrating the exceptional speed and scalability of polariton-based XY simulators.

cond-mat.mes-hall↗

arXiv2024

Exciton-Enhanced Superconductivity in Monolayer Films of Aluminum

The BCS theory has achieved widespread success in describing conventional superconductivity. However, when the length scale reaches the atomic limit, the reduced dimensionality may lead to the quantum breakdown resulting in unpredictable superconducting behaviors. It has been exper imentally evidenced that the critical temperature is strongly enhanced in the monolayer films of FeSe/STO and epitaxial Aluminum. Here, we propose the exciton mechanism of superconductivity as a possible reason for the enhanced superconductivity in hybrid superconductor-semiconductor structures. The exciton-induced Cooper pairing may lead to the larger energy gaps and higher critical temperatures as compared to those caused by the phonon induced superconductivity. A detailed comparison of the theory and experimental results of Ref. 1 reveals the possibility of exciton-induced superconductivity in thin films of Aluminum near the monolayer limit.

cond-mat.supr-con↗

arXiv2023

The interplay between exciton- and phonon-induced superconductivity might explain the phenomena observed in LK-99

The experimental results hinting at the room temperature and ambient pressure superconductivity and magnetic levitation in LK-99 attracted an unprecedented interest. While attempts of other teams to reproduce the reported observations on similar samples failed so far, it seems worthwhile to try building a theoretical model that would explain the ensemble of the available data. One of important features that needs to be explained is an apparent contradiction between an extremely high critical temperature Tc and rather modest critical magnetic field Bc and critical current jc reported for LK-99. We show theoretically, that these data may be quantitatively reproduced assuming the interplay between exciton- and phonon-induced superconductivity, while the conventional BCS or Brinkman-Rice-Bardeen-Cooper-Schriefer (BR-BCS) mechanisms would result in a much higher Bc for the same Tc.

cond-mat.supr-con↗