Mobile impurity near the superfluid-Mott insulator quantum critical point in two dimensions

TL;DR

This paper studies how a mobile impurity behaves near the superfluid-Mott insulator quantum critical point in two dimensions, revealing a transition from quantum spreading to classical diffusion influenced by critical fluctuations.

Contribution

It introduces a theoretical framework for impurity dynamics at the superfluid-insulator transition, highlighting the role of dangerously irrelevant perturbations in two-dimensional quantum critical systems.

Findings

Impurity exhibits quantum wave packet spreading at short times.

Impurity transitions to Brownian diffusion at long times.

Dynamics governed by interplay of critical fluctuations and irrelevant perturbations.

Abstract

We consider bosonic atoms in an optical lattice at integer filling, tuned to the superfluid-Mott insulator critical point, and coupled to a single, mobile impurity atom of a different species. This setup is inspired by current experiments with quantum gas microscopes, which enable tracking of the impurity motion. We describe the evolution of the impurity motion from quantum wave packet spread at short times, to Brownian diffusion at long times. This dynamics is controlled by the interplay between dangerously irrelevant perturbations at the strongly-interacting field theory describing the superfluid-insulator transition in two spatial dimensions.