Susceptibility of the transverse field Ising model on the square lattice

TL;DR

This paper numerically investigates the susceptibility of the transverse field Ising model on a square lattice, revealing critical behavior and crossovers near the quantum critical point across various temperatures and fields.

Contribution

It introduces a universal expression with a constant π that accurately describes susceptibility near the quantum critical point, highlighting two temperature-dependent crossovers.

Findings

The susceptibility follows a universal asymptotic form near the quantum critical point.

Two distinct crossovers in behavior are observed as temperature varies.

The critical transverse field and exponent are determined by a single constant π.

Abstract

Susceptibility of the transverse field Ising model on the square lattice is calculated numerically in the paramagnetic phase in a wide range of temperatures and transverse fields. An expression with one constant $\pi$, that determines both the critical exponent $\gamma$ and the critical transverse field, compellingly represents the data asymptotically near the quantum critical point, except for a narrow classical region close to the phase transition line, and shows two crossovers as temperature varies.