Long-range random transverse-field Ising model in three dimensions

TL;DR

This paper investigates the phase transition in a three-dimensional long-range random transverse-field Ising model, revealing a mixed-order transition characterized by logarithmic scaling and finite limiting magnetization.

Contribution

It introduces a numerical analysis of the phase transition in 3D long-range RFIM using a strong disorder renormalization group, highlighting the mixed-order nature of the transition.

Findings

Sample-dependent pseudo-critical points scale with 1/ln L

Critical magnetization scales with (ln L)^χ / L^d

Excitation energy scales as L^(-α)

Abstract

We consider the random transverse-field Ising model in $d=3$ dimensions with long-range ferromagnetic interactions which decay as a power $\alpha > d$ with the distance. Using a variant of the strong disorder renormalization group method we study numerically the phase-transition point from the paramagnetic side. The distribution of the (sample dependent) pseudo-critical points is found to scale with $1/\ln L$, $L$ being the linear size of the sample. Similarly, the critical magnetization scales with $(\ln L)^{\chi}/L^d$ and the excitation energy behaves as $L^{-\alpha}$. Using extreme-value statistics we argue that extrapolating from the ferromagnetic side the magnetization approaches a finite limiting value and thus the transition is of mixed-order.