Near-frozen nonequilibrium state at high energy in an integrable system

Ergodic many-body systems are expected to reach thermal equilibrium. Here, we demonstrate that, surprisingly, high-energy electrons, which are injected into a quantum Hall edge mode with finite-range interactions, stabilize at a far-from-thermalized state over a long timescale. To detect this nonequilibrium state, one positions an energy-resolved detector downstream of the injection point. So far, nonequilibrium distributions in integrable systems were either found not to display relaxation at all, or generically relax to near-thermal asymptotic states. In stark contrast, the here-obtained many-body state comprises fast-decaying transient components, followed by a nearly frozen distribution with a peak near the injection energy.