Site-resolved imaging of a fermionic Mott insulator

TL;DR

This study demonstrates site-resolved imaging of fermionic quantum phases in optical lattices, revealing detailed insights into Mott insulators, metals, and band insulators at the microscopic level, with implications for understanding complex quantum systems.

Contribution

First to achieve site-resolved imaging of fermionic Mott insulators, metals, and band insulators, providing detailed local measurements of quantum phases in ultracold atom systems.

Findings

Observation of over 400 atoms in 2D Mott insulators.

Detection of phase coexistence at intermediate interactions.

Measurement of local entropies as low as 0.5 k_B in band insulators.

Abstract

The complexity of quantum many-body systems originates from the interplay of strong interactions, quantum statistics, and the large number of quantum-mechanical degrees of freedom. Probing these systems on a microscopic level with single-site resolution offers important insights. Here we report site-resolved imaging of two-component fermionic Mott insulators, metals, and band insulators using ultracold atoms in a square lattice. For strong repulsive interactions we observe two-dimensional Mott insulators containing over 400 atoms. For intermediate interactions, we observe a coexistence of phases. From comparison to theory we find trap-averaged entropies per particle of $1.0\,k_{\mathrm{B}}$. In the band-insulator we find local entropies as low as $0.5\,k_{\mathrm{B}}$. Access to local observables will aid the understanding of fermionic many-body systems in regimes inaccessible by modern theoretical methods.