Pigneur, Marine

Date:   Tuesday, March 3, 2020
Time:   14:00
Place:   ETH Zurich, Hönggerberg, HCI D 4
Host:    Tilman Esslinger

Relaxation to a Phase-locked Equilibrium State in a One-dimensional Bosonic Josephson Junction

Marine Pigneur
Atominstitut, TU Wien, Austria

The relaxation of isolated quantum many-body systems is a major unsolved problem of modern physics, which connects to many fundamental questions. However, realizations of quantum many-body systems which are both well isolated from their environment and accessible to experimental study are scarce. In recent years, the field has experienced rapid progress, partly attributed to ultra-cold atoms.

I will present the experimental study of a relaxation phenomenon occurring in a one-dimensional bosonic Josephson junction [1]. The system consists of two 1D quasi Bose-Einstein condensates of ⁸⁷Rb, magnetically trapped on an atom chip. Using radio-frequency dressing, we deform a single harmonic trap, in which the atoms are initially condensed, into a double-well potential and realize a splitting of the wave function. A large spatial separation and a tilt of the double-well enable us to prepare a broad variety of initial states by precisely adjusting the initial population and relative phase of the two wave packets, while preserving the phase coherence. By re-coupling the two wave packets, we investigate tunneling regimes such as Josephson (plasma) oscillations and macroscopic quantum self-trapping.

In both regimes, we observe that the tunneling dynamics exhibits a relaxation to a phase-locked equilibrium state contradicting theoretical predictions [2]. We support the experimental results with an empirical model [3] that allows quantitative discussions according to various experimental parameters. Our results illustrate how strongly the non-equilibrium dynamics differ from the equilibrium one, which is well described by thermodynamics and statistical physics.

[1] M. Pigneur et al. PRL 120, 173601 (2018)
[2] D.X. Horvath et al. PRA 100, 013613 (2019)
[3] M. Pigneur et al. PRA 98, 063632 (2018)