Signatures of a non-thermal metastable state in copropagating quantum Hall edge channels

A Tomonaga-Luttinger (TL) liquid is known as an integrable system, in which a non-equilibrium many-body state survives without relaxing to a thermalized state. This intriguing characteristic is tested experimentally in copropagating quantum Hall edge channels at bulk filling factor nu = 2. The unidirectional transport allows us to investigate the time evolution by measuring the spatial evolution of the electronic states. The initial state is prepared with a biased quantum point contact, and its spatial evolution is measured with a quantum-dot energy spectrometer. We find strong evidences for a non-thermal metastable state in agreement with the TL theory before the system relaxes to thermal equilibrium with coupling to the environment.