Anisotropic quantum quench in the presence of frustration or background gauge fields: A probe of bulk currents and topological chiral edge modes

TL;DR

This paper proposes a gauge-invariant method using anisotropic quenches to visualize bulk and edge currents in ultracold atomic systems with artificial gauge fields, applicable to various particle types and topological states.

Contribution

It introduces a general scheme for detecting equilibrium current patterns and chiral edge currents via density modulations after anisotropic quenches in lattice systems.

Findings

The method visualizes bulk current patterns in superfluid and normal fermionic systems.

It detects chiral edge currents in topological insulators.

The scheme is independent of particle statistics.

Abstract

Bosons and fermions, in the presence of frustration or background gauge fields, can form manybody ground states that support equilibrium 'charge' or 'spin' currents. Motivated by the experimental creation of frustration or artificial gauge fields in ultracold atomic systems, we propose a general scheme by which making a sudden anisotropic quench of the atom tunneling across the lattice and tracking the ensuing density modulations provides a powerful and gauge invariant route to visualizing diverse equilibrium current patterns. Using illustrative examples of trapped superfluid Bose and normal Fermi systems in the presence of artificial magnetic fluxes on square lattices, and frustrated bosons in a triangular lattice, we show that this scheme to probe equilibrium bulk current order works independent of particle statistics. We also show that such quenches can detect chiral edge currents in gapped topological states, such as quantum Hall or quantum spin Hall insulators.