Enhanced decoherence in the vicinity of a phase transition

TL;DR

This paper investigates how a central spin's decoherence is significantly enhanced near a zero-temperature phase transition in two-dimensional ferromagnetic and antiferromagnetic environments, highlighting critical fluctuations' impact.

Contribution

It demonstrates that critical fluctuations near a quantum phase transition accelerate decoherence of a central spin, with maximal decoherence occurring at zero temperature.

Findings

Decoherence rate diverges at zero temperature.

Decoherence increases as the system approaches the phase transition.

Critical fluctuations enhance decoherence near the transition.

Abstract

We study the decoherence of a spin-1/2 induced by an environment which is on the verge of a continuous phase transition. We consider spin environments described by the ferromagnetic and antiferromagnetic Heisenberg models on a square lattice. As is well known, these two dimensional systems undergo a continuous phase transition at zero temperature, where, the spins order spontaneously. For weak coupling of the central spin to these baths, we find that as one approaches the transition temperature, critical fluctuations make the central spin decohere faster. Furthermore, the decoherence is maximal at zero temperature as signalled by the divergence of the Markovian decoherence rate.