Abstract

We study the competition between fermion pairing, magnetism, and charge order in a spin-imbalanced attractive Hubbard gas of fermionic 40K atoms realized in a single 2D plane of an optical lattice. Using spin- and atom-resolved quantum gas microscopy, we track densities, doublons, singlons, magnetization, and spin fluctuations across a range of densities, magnetizations, and interaction strengths. We compare the measurements with auxiliary-field quantum Monte Carlo and numerical linked-cluster expansion calculations and find evidence for coexistence of nonlocal fermion pairs and excess fermions at weak imbalance, a Bose-Fermi mixture at stronger attraction, a crossover from charge-density-wave correlations to a Fermi liquid of polarons under spin doping, and possible signatures of combined spin- and pair-density-wave order at the highest imbalance and interaction strength.

Abstract

We study the competition between fermion pairing, magnetism, and charge order in a spin-imbalanced attractive Hubbard gas of fermionic 40K atoms realized in a single 2D plane of an optical lattice. Using spin- and atom-resolved quantum gas microscopy, we track densities, doublons, singlons, magnetization, and spin fluctuations across a range of densities, magnetizations, and interaction strengths. We compare the measurements with auxiliary-field quantum Monte Carlo and numerical linked-cluster expansion calculations and find evidence for coexistence of nonlocal fermion pairs and excess fermions at weak imbalance, a Bose-Fermi mixture at stronger attraction, a crossover from charge-density-wave correlations to a Fermi liquid of polarons under spin doping, and possible signatures of combined spin- and pair-density-wave order at the highest imbalance and interaction strength.

Abstract

We study the competition between fermion pairing, magnetism, and charge order in a spin-imbalanced attractive Hubbard gas of fermionic 40K atoms realized in a single 2D plane of an optical lattice. Using spin- and atom-resolved quantum gas microscopy, we track densities, doublons, singlons, magnetization, and spin fluctuations across a range of densities, magnetizations, and interaction strengths. We compare the measurements with auxiliary-field quantum Monte Carlo and numerical linked-cluster expansion calculations and find evidence for coexistence of nonlocal fermion pairs and excess fermions at weak imbalance, a Bose-Fermi mixture at stronger attraction, a crossover from charge-density-wave correlations to a Fermi liquid of polarons under spin doping, and possible signatures of combined spin- and pair-density-wave order at the highest imbalance and interaction strength.

Abstract

We study the competition between fermion pairing, magnetism, and charge order in a spin-imbalanced attractive Hubbard gas of fermionic 40K atoms realized in a single 2D plane of an optical lattice. Using spin- and atom-resolved quantum gas microscopy, we track densities, doublons, singlons, magnetization, and spin fluctuations across a range of densities, magnetizations, and interaction strengths. We compare the measurements with auxiliary-field quantum Monte Carlo and numerical linked-cluster expansion calculations and find evidence for coexistence of nonlocal fermion pairs and excess fermions at weak imbalance, a Bose-Fermi mixture at stronger attraction, a crossover from charge-density-wave correlations to a Fermi liquid of polarons under spin doping, and possible signatures of combined spin- and pair-density-wave order at the highest imbalance and interaction strength.