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

Abstract

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.

Figures (4)

• Figure 1: (a) Schematic of the polariton condensate under two resonant oblique pumping beams. (b) Flow ($v_F$) and sound velocity ($c_s$) profile. The acoustic horizon is created at the transonic point $x=0\ \rm \mu m$. $v_F$ and $c_s$ can be precisely controlled by the amplitude and incidence angle of the resonant pump, respectively.
• Figure 2: (a) Classification diagram of wave regions in the $(\rho_0, v_0)$ plane. The different wave regions are labeled with circled numbers. (b) Schematic diagram showing the existence regions of different wave solutions in the $(\rho_0, \alpha, v_0)$ space, which vary with the parameter $\alpha$. The black dashed line represents the positions of all intersection points $(\rho_R, v_R)$ for different values of $\alpha$.
• Figure 3: (a) Distribution of Riemann invariants; (b) Waveform structure of the density $\rho$; (c) Spatiotemporal evolution of the density $\rho$ up to $\tau=4$; In (b), the red dashed and blue solid lines represent the theoretical and numerical results, respectively. (d) Comparison between numerical results of flow velocity and sound speed; In (d), the orange dash-dotted line represents the sound speed, and the blue solid line represents the flow velocity. (a), (b), and (d) present the results at $\tau = 2$. The parameters are $\alpha=2$, $(\rho_R, v_R)=(0.5,1)$, and $(\rho_0, v_0)=(4,1)$.
• Figure 4: (a) Second order correlation function $g^{(2)}(x,x^\prime)$. The off-diagonal curve shows a negative correlation as a signature of the quantum noise passing through the acoustic horizon. (b) The distributions of the Hawking radiation calculated from the correlation function in the dashed box of (a) (blue solid curve), and from the surface gravity (red dashed curve). Parameters: $m^*=5\times10^{-5}m_e$, $g\rho_0=0.1\ \rm meV$, $\phi(x<0,t=0)=2\sqrt{\rho_0}e^{-ik_Lx}$, $\phi(x\geq0,t=0)=\sqrt{\rho_0}e^{-ik_Rx}$, $k_L=0.51\ \rm \mu m^{-1}$, $k_R=0.78\ \rm \mu m^{-1}$