Hydrodynamic stabilization of self-organized criticality in a driven Rydberg gas

TL;DR

This paper investigates how hydrodynamic effects stabilize self-organized criticality in a driven ultracold Rydberg gas, revealing a feedback mechanism that sustains criticality and produces characteristic density profiles.

Contribution

It uncovers a hydrodynamic feedback mechanism that extends the critical region in a driven Rydberg gas, enhancing understanding of SOC robustness in thermal environments.

Findings

Hydrodynamic transport sustains criticality in the gas.

Extended critical region with flat-top density profile observed.

Feedback mechanism compensates for atom loss during avalanches.

Abstract

Signatures of self-organized criticality (SOC) have recently been observed in an ultracold atomic gas under continuous laser excitation to strongly-interacting Rydberg states [S. Helmrich et al., Nature, 577, 481--486 (2020)]. This creates a unique possibility to study this intriguing dynamical phenomenon, e.g., to probe its robustness and universality, under controlled experimental conditions. Here we examine the self-organizing dynamics of a driven ultracold gas and identify an unanticipated feedback mechanism, which is especially important for systems coupled to thermal baths. It sustains an extended critical region in the trap center for a notably long time via hydrodynamic transport of particles from the flanks of the cloud toward the center. This compensates the avalanche-induced atom loss and leads to a characteristic flat-top density profile, providing an additional experimental signature for SOC and minimizing effects of inhomogeneity on the SOC features.