Dynamics of spatial phase coherence in a dissipative Bose-Hubbard atomic system

TL;DR

This study examines how spatial coherence in a dissipative Bose-Hubbard system decays over time, revealing a power-law behavior due to the interplay of fluorescence-induced decoherence and tunneling.

Contribution

It provides the first experimental observation of power-law decay of spatial correlations in a dissipative many-body quantum system, confirming theoretical predictions.

Findings

Power-law decay of nearest-neighbor correlator with exponent ~0.54

Correlation between n-n and n-n-n correlators as C2 ≈ C1^2

Agreement with dissipative Bose-Hubbard model predictions

Abstract

We investigate the loss of spatial coherence of one-dimensional bosonic gases in optical lattices illuminated by a near-resonant excitation laser. Because the atoms recoil in a random direction after each spontaneous emission, the atomic momentum distribution progressively broadens. Equivalently, the spatial correlation function (the Fourier-conjugate quantity of the momentum distribution) progressively narrows down as more photons are scattered. Here we measure the correlation function of the matter field for fixed distances corresponding to nearest-neighbor (n-n) and next-nearest-neighbor (n-n-n) sites of the optical lattice as a function of time, hereafter called n-n and n-n-n correlators. For strongly interacting lattice gases, we find that the n-n correlator $C_1$ decays as a power-law at long times, $C_1\propto 1/t^{\alpha}$, in stark contrast with the exponential decay expected for independent particles. The power-law decay reflects a non-trivial dissipative many-body dynamics, where interactions change drastically the interplay between fluorescence destroying spatial coherence, and coherent tunnelling between neighboring sites restoring spatial coherence at short distances. The observed decay exponent $\alpha \approx 0.54(6) $ is in good agreement with the prediction $\alpha=1/2$ from a dissipative Bose-Hubbard model accounting for the fluorescence-induced decoherence. Furthermore, we find that the n-n correlator $C_1$ controls the n-n-n correlator $C_2$ through the relation $C_2 \approx C_1^2$, also in accordance with the dissipative Bose-Hubbard model.