Influence of superohmic dissipation on a disordered quantum critical point

TL;DR

This paper studies how superohmic dissipation affects a disordered quantum critical point, revealing a Kosterlitz-Thouless transition with power-law scaling and analyzing critical behavior using strong-disorder renormalization group methods.

Contribution

It provides an exact analysis of the critical behavior in one dimension for a disordered quantum system with superohmic dissipation, highlighting a novel transition type.

Findings

Superohmic dissipation leads to a Kosterlitz-Thouless transition.

The dynamical critical exponent varies with the bath's spectral density.

Power-law dynamical scaling is observed at the transition.

Abstract

We investigate the combined influence of quenched randomness and dissipation on a quantum critical point with O(N) order-parameter symmetry. Utilizing a strong-disorder renormalization group, we determine the critical behavior in one space dimension exactly. For superohmic dissipation, we find a Kosterlitz-Thouless type transition with conventional (power-law) dynamical scaling. The dynamical critical exponent depends on the spectral density of the dissipative baths. We also discuss the Griffiths singularities, and we determine observables.