Dissipation effects in random transverse-field Ising chains

TL;DR

This paper analyzes how different types of dissipation affect the quantum phase transition in a disordered transverse-field Ising chain, revealing that Ohmic and sub-Ohmic damping smear the transition while super-Ohmic damping leaves it unchanged.

Contribution

It provides an analytical strong-disorder renormalization-group study of dissipation effects on quantum criticality in disordered chains, highlighting the distinct impacts of various damping types.

Findings

Ohmic damping destroys the infinite-randomness critical point.

Sub-Ohmic dissipation also leads to a smeared transition.

Super-Ohmic damping does not alter the critical behavior.

Abstract

We study the effects of Ohmic, super-Ohmic, and sub-Ohmic dissipation on the zero-temperature quantum phase transition in the random transverse-field Ising chain by means of an (asymptotically exact) analytical strong-disorder renormalization-group approach. We find that Ohmic damping destabilizes the infinite-randomness critical point and the associated quantum Griffiths singularities of the dissipationless system. The quantum dynamics of large magnetic clusters freezes completely which destroys the sharp phase transition by smearing. The effects of sub-Ohmic dissipation are similar and also lead to a smeared transition. In contrast, super-Ohmic damping is an irrelevant perturbation; the critical behavior is thus identical to that of the dissipationless system. We discuss the resulting phase diagrams, the behavior of various observables, and the implications to higher dimensions and experiments.