Homogeneous fermionic Hubbard gases in a flat-top optical lattice

TL;DR

This study creates a large, homogeneous fermionic Hubbard gas in an optical lattice, enabling precise measurements of quantum phases and correlations, including the metal-insulator transition and antiferromagnetic effects.

Contribution

We developed a hybrid optical potential to realize a homogeneous fermionic Hubbard system across millions of lattice sites, allowing detailed exploration of quantum many-body phenomena.

Findings

Observation of the metal to Mott insulator crossover via doublon fraction D

Detection of non-monotonic temperature dependence indicating Pomeranchuk effect

Alignment of experimental data with zero-temperature Hubbard model calculations

Abstract

Fermionic atoms in a large-scale, homogeneous optical lattice provide an ideal quantum simulator for investigating the fermionic Hubbard model, yet achieving this remains challenging. Here, by developing a hybrid potential that integrates a flat-top optical lattice with an optical box trap, we successfully realize the creation of three-dimensional, homogeneous fermionic Hubbard gases across approximately $8\times10^5$ lattice sites. This homogeneous system enables us to capture a well-defined energy band occupation that aligns perfectly with the theoretical calculations for a zero-temperature, ideal fermionic Hubbard model. Furthermore, by employing novel radio-frequency spectroscopy, we precisely measure the doublon fraction $D$ as a function of interaction strength $U$ and temperature $T$, respectively. The crossover from metal to Mott insulator is detected, where $D$ smoothly decreases with increasing $U$. More importantly, we observe a non-monotonic temperature dependence in $D$, revealing the Pomeranchuk effect and the development of extended antiferromagnetic correlations.