Rounding of a first-order quantum phase transition to a strong-coupling critical point

TL;DR

This paper shows that quenched disorder transforms first-order quantum phase transitions into continuous ones in the quantum Ashkin-Teller model, revealing a new type of infinite-randomness critical point with unique properties.

Contribution

It demonstrates how quenched disorder rounds first-order quantum phase transitions into continuous ones and characterizes a novel infinite-randomness critical point in the strong coupling regime.

Findings

Disorder rounds first-order transitions to continuous ones.

Identification of a new infinite-randomness critical point.

Detailed analysis of critical properties in the strong coupling case.

Abstract

We investigate the effects of quenched disorder on first-order quantum phase transitions on the example of the $N$-color quantum Ashkin-Teller model. By means of a strong-disorder renormalization group, we demonstrate that quenched disorder rounds the first-order quantum phase transition to a continuous one for both weak and strong coupling between the colors. In the strong coupling case, we find a distinct type of infinite-randomness critical point characterized by additional internal degrees of freedom. We investigate its critical properties in detail, and we discuss broader implications for the fate of first-order quantum phase transitions in disordered systems.