Tunable nanomagnetism in moderately cold fermions on optical lattices

TL;DR

This paper investigates how localized defects in the Hubbard model on optical lattices influence magnetic correlations, revealing tunable nanomagnetism that persists at higher temperatures and can be used for thermometry in cold-atom experiments.

Contribution

It demonstrates the emergence of tunable nanomagnetism in cold-atom systems with impurities, using exact quantum Monte Carlo simulations, highlighting potential for experimental observation and thermometry.

Findings

Enhanced magnetic correlations at impurity sites due to interactions or reduced environmental coupling

Persistence of magnetic correlations at elevated temperatures

Potential application as robust thermometers in cold-atom experiments

Abstract

Localized defects, unavoidable in real solids, may be simulated in (generically defect-free) cold-atom systems, e.g., via modifications of the optical lattice. We study the Hubbard model on a square lattice with single impurities, pairs of nearby impurities, or lines of impurities using numerically exact determinantal quantum Monte Carlo simulations. In all cases, correlations on the "impurity" sites are enhanced either by larger on-site interactions or by a reduced coupling to the environment. We find highly nontrivial magnetic correlations, which persist at elevated temperatures and should be accessible in cold-atom systems with current experimental techniques. With improved cooling techniques, these features could be followed towards generic quantum antiferromagnetism in the homogeneous limit. More generally, tunable crossing points between different correlation functions could be used, in a quantum steelyard balance setup, as robust thermometers.