Mott glass phase in a diluted bilayer Heisenberg quantum antiferromagnet

TL;DR

This study uses quantum Monte Carlo simulations to map the phase diagram of a diluted bilayer Heisenberg antiferromagnet, revealing a novel gapless Mott glass phase with unique susceptibility properties and distinct critical behavior from the clean system.

Contribution

It identifies and characterizes a gapless Mott glass phase in a diluted bilayer Heisenberg model, showing its unique properties and critical exponents differ from the clean system.

Findings

Discovery of a gapless Mott glass phase with vanishing uniform susceptibility.

The quantum glass phase exhibits a stretched exponential susceptibility at finite temperature.

Critical exponents at the Néel to Mott glass transition differ from the standard O(3) universality class.

Abstract

We use quantum Monte Carlo simulations to study a dimer-diluted $S=1/2$ Heisenberg model on a bilayer square lattice with intralayer interaction $J_{1}$ and interlayer interaction $J_{2}$. Below the classical percolation threshold $p_c$, the system has three phases reachable by tuning the interaction ratio $g=J_{2}/J_{1}$: a N$\acute{e}$el ordered phase, a gapless quantum glass phase, and a gapped quantum paramagnetic phase. We present the ground-state phase diagram in the plane of dilution $p$ and interaction ratio $g$. The quantum glass phase is certified to be of the gapless Mott glass type, having a uniform susceptibility vanishing at zero temperature $T$ and following a stretched exponential form at $T>0$; $\chi_u \sim \exp(-b/T^{\alpha})$ with $\alpha < 1$. At the phase transition point from N$\acute{e}$el ordered to Mott glass, we find that the critical exponents are different from those of the clean system described by the standard $O(3)$ universality class in 2+1 dimensions.