Band and correlated insulators of cold fermions in a mesoscopic lattice

TL;DR

This paper demonstrates control over quantum-coherent transport in a one-dimensional fermionic system with a tunable optical lattice, revealing a persistent insulating phase influenced by interactions, and providing a platform for studying non-equilibrium many-body physics.

Contribution

It introduces a controllable, site-specific optical lattice in a fermionic quantum wire and investigates the persistence of insulating states under varying interactions, supported by theoretical analysis.

Findings

Observation of a band insulating phase in a mesoscopic lattice.

Insulating state persists under strong attractive interactions.

Qualitative agreement between experiments and bosonization plus Monte Carlo simulations.

Abstract

We investigate the transport properties of neutral, fermionic atoms passing through a one-dimensional quantum wire containing a mesoscopic lattice. The lattice is realized by projecting individually controlled, thin optical barriers on top of a ballistic conductor. Building an increasingly longer lattice, one site after another, we observe and characterize the emergence of a band insulating phase, demonstrating control over quantum-coherent transport. We explore the influence of atom-atom interactions and show that the insulating state persists as contact interactions are tuned from moderately to strongly attractive. Using bosonization and classical Monte-Carlo simulations we analyze such a model of interacting fermions and find good qualitative agreement with the data. The robustness of the insulating state supports the existence of a Luther-Emery liquid in the one-dimensional wire. Our work realizes a tunable, site-controlled lattice Fermi gas strongly coupled to reservoirs, which is an ideal test bed for non-equilibrium many-body physics.