Discriminating antiferromagnetic signatures in ultracold fermions by tunable geometric frustration

TL;DR

This paper demonstrates how tunable geometric frustration in optical lattices affects antiferromagnetic correlations in ultracold fermions, providing a pathway for experimental detection of antiferromagnetism.

Contribution

It introduces a method to distinguish frustration effects from bandwidth changes in the Hubbard model using determinant quantum Monte Carlo simulations.

Findings

Frustration enhances double occupancy, indicating suppression of antiferromagnetic correlations.

Proper rescaling isolates frustration effects from bandwidth variations.

Results suggest feasible experimental detection of antiferromagnetism in ultracold fermions.

Abstract

Recently, it has become possible to tune optical lattices continuously between square and triangular geometries. We compute thermodynamics and spin correlations in the corresponding Hubbard model using determinant quantum Monte Carlo and show that the frustration effects induced by the variable hopping terms can be clearly separated from concomitant bandwidth changes by a proper rescaling of the interaction. An enhancement of the double occupancy by geometric frustration signals the destruction of nontrivial antiferromagnetic correlations at weak coupling and entropy $s\lesssim \ln(2)$ (and restores Pomeranchuk cooling at strong frustration), paving the way to the long-sought experimental detection of antiferromagnetism in ultracold fermions on optical lattices.