Infinite-randomness quantum critical points induced by dissipation

TL;DR

This paper develops a strong-disorder renormalization group approach to study quantum phase transitions with O(N) symmetry under disorder and dissipation, revealing an infinite-randomness fixed point for Ohmic dissipation.

Contribution

It introduces a novel renormalization group method to analyze the effects of dissipation on quantum critical points with continuous symmetry, identifying a new universality class.

Findings

Transition governed by an infinite-randomness fixed point

Critical behavior characterized for Ohmic dissipation

Analysis of quantum Griffiths phase

Abstract

We develop a strong-disorder renormalization group to study quantum phase transitions with continuous O$(N)$ symmetry order parameters under the influence of both quenched disorder and dissipation. For Ohmic dissipation, as realized in Hertz' theory of the itinerant antiferromagnetic transition or in the superconductor-metal transition in nanowires, we find the transition to be governed by an exotic infinite-randomness fixed point in the same universality class as the (dissipationless) random transverse-field Ising model. We determine the critical behavior and calculate key observables at the transition and in the associated quantum Griffiths phase. We also briefly discuss the cases of superohmic and subohmic dissipations.