Interference and short-range correlation in fermionic Hubbard gases

TL;DR

This paper reports the observation and analysis of interference patterns in ultracold fermionic Hubbard gases, revealing short-range correlations and a metal-insulator crossover, with results matching quantum Monte Carlo simulations.

Contribution

It introduces a new method to extract first-order correlations from interference patterns in fermionic gases, advancing the understanding of short-range correlations in strongly correlated systems.

Findings

Observation of interference patterns in fermionic Hubbard gases.

Mapping of nearest-neighbor correlations across different fillings and interactions.

Correlation measurements agree with quantum Monte Carlo calculations.

Abstract

The interference patterns of ultracold atoms, observed after ballistic expansion from optical lattices, encode essential information about strongly correlated lattice systems, including phase coherence and non-local correlations. While the interference of lattice bosons has been extensively investigated, quantitative studies of the lattice fermion interference remain challenging. Here, we report the observation and quantitative characterization of interference patterns in low-temperature, homogeneous fermionic Hubbard gases. We develop a novel method to extract first-order correlations from interference patterns, which directly reflect the short-range phase coherence of lattice fermions. Mapping the nearest-neighbor correlations as a function of lattice filling and interaction strength, we observe a crossover from a metal to a Mott insulator. Moreover, at half filling, the measured correlations agree well with quantum Monte Carlo calculations and remain finite in the regime of strong repulsion, revealing virtual tunneling processes driven by quantum fluctuations.