Quantum Monte Carlo simulations of highly frustrated magnets in a cluster basis: The two-dimensional Shastry-Sutherland model

TL;DR

This paper introduces a cluster basis approach in Quantum Monte Carlo simulations to mitigate the sign problem, enabling efficient study of highly frustrated magnets like the two-dimensional Shastry-Sutherland model.

Contribution

The authors demonstrate how choosing an appropriate cluster basis can reduce or eliminate the sign problem in QMC simulations of frustrated magnets.

Findings

Cluster basis reduces sign problem in QMC simulations.

Application to the Shastry-Sutherland model shows improved simulation efficiency.

Enables thermodynamic studies of previously inaccessible frustrated systems.

Abstract

Quantum Monte Carlo (QMC) simulations constitute nowadays one of the most powerful methods to study strongly correlated quantum systems, provided that no "sign problem" arises. However, many systems of interest, including highly frustrated magnets, suffer from an average sign that is close to zero in standard QMC simulations. Nevertheless, a possible sign problem depends on the simulation basis, and here we demonstrate how a suitable choice of cluster basis can be used to eliminate or at least reduce the sign problem in highly frustrated magnets that were so far inaccessible to efficient QMC simulations. We focus in particular on the application of a two-spin (dimer)-based QMC method to the thermodynamics of the spin-1/2 Shastry-Sutherland model for SrCu$_2$(BO$_3$)$_2$.