Effect of random interactions in spin baths on decoherence

TL;DR

This paper investigates how random interactions within spin baths influence the decoherence of a central spin, revealing that interactions can reduce decoherence and induce non-Markovian effects, especially at low temperatures.

Contribution

It provides analytic results for Ising spin baths with random interactions, demonstrating the impact of intrabath interactions on decoherence and non-Markovian behavior.

Findings

Interactions reduce decoherence in higher-dimensional lattices.

Decoherence is governed by local-field distribution and structure factor.

Saturation of decay rate occurs at high temperatures, unlike bosonic baths.

Abstract

We study the decoherence of a central spin 1/2 induced by a spin bath with intrabath interactions. Since we are interested in the cumulative effect of interaction and disorder, we study baths comprising Ising spins with random ferro- and antiferromagnetic interactions between the spins. Using the resolvent operator method which goes beyond the standard Born-Markov master equation approach, we show that, in the weak coupling regime, the decoherence of the central spin at all times is entirely determined by the local-field distribution or equivalently, the dynamical structure factor of the Ising bath. We present analytic results for the Ising spin chain bath at arbitrary temperature for different distributions of the intrabath interaction strengths. We find clear evidence of non-Markovian behavior in the low temperature regime. We also consider baths described by Ising models on higher-dimensional lattices. We find that interactions lead to a significant reduction of the decoherence. An important feature of interacting spinbaths is the saturation of the asymptotic Markovian decay rate at high temperatures, as opposed to the conventional Ohmic boson bath.