Solution to sign problems in models of interacting fermions and quantum spins

TL;DR

This paper presents new methods to solve fermion sign problems in models with interacting fermions and quantum spins, extending the class of solvable strongly correlated systems using worldline and meron-cluster techniques.

Contribution

It introduces a novel approach that combines worldline representations and meron-cluster methods to overcome sign problems in complex fermion-spin models.

Findings

Sign problems are solvable in certain fermion-spin models using worldline representation.

The combined approach extends the range of models with manageable sign issues.

Demonstrated solutions in several strongly correlated systems.

Abstract

We show that solutions to fermion sign problems in the CT-INT formulation can be extended to systems involving fermions interacting with dynamical quantum spins. While these sign problems seem unsolvable in the auxiliary field approach, solutions emerge in the worldline representation of quantum spins. Combining the idea with meron-cluster methods, we are able to extend the solvable models even further. We demonstrate these novel solutions to sign problems by considering several examples of strongly correlated systems.