Quantum Monte Carlo study of the two-dimensional ferromagnet

TL;DR

This paper uses Quantum Monte Carlo simulations to investigate the nature of the ferromagnetic phase transition in a two-dimensional Stoner model, revealing how screening length influences the order of the transition and its critical interaction strength.

Contribution

It provides the first detailed Quantum Monte Carlo analysis of the paramagnet-ferromagnet transition in 2D, highlighting the effects of interaction screening on transition order and critical parameters.

Findings

Short screening lengths lead to a first order transition.

Longer screening lengths result in a second order transition.

Critical interaction strength increases with screening length.

Abstract

We present Quantum Monte Carlo calculations that probe the paramagnet-ferromagnet phase transition in a two-dimensional Stoner Hamiltonian. With a screened Coulomb interaction we observe a first order ferromagnetic transition for short screening lengths, and a second order transition with a longer screening length, accompanied by a rising critical interaction strength. Finally, we discuss the consequences of our results for an ultracold atomic gas with finite ranged interactions.