Phase transition in fluctuations of interacting spins at infinite temperature

TL;DR

This paper reveals a phase transition in the fluctuation behavior of interacting spins at infinite temperature, where the spin noise spectrum exhibits discontinuous changes driven by an external magnetic field, indicating nontrivial dynamics despite high temperature.

Contribution

It demonstrates a novel phase transition in spin noise spectra at infinite temperature, linking fluctuation dynamics to external magnetic fields in a long-range interacting spin model.

Findings

Spin noise power spectrum can change discontinuously with magnetic field.

A phase transition occurs associated with the disappearance of a noise peak.

The transition affects decoherence mechanisms in spin systems.

Abstract

The high temperature limit of interacting spins is usually not associated with ordering or critical phenomena. Nevertheless, spontaneous fluctuations of a local spin polarization at equilibrium have nontrivial dynamics even in this limit. Here, we demonstrate that the spin noise power spectrum of these fluctuations can undergo discontinuous changes as a function of an external magnetic field. As a simple illustration, we consider a model of Ising-like long range spin-spin interactions with a transverse magnetic field as a control parameter. This system undergoes a phase transition associated with disappearance of the noise power peak responsible for the most detrimental decoherence effect of the interactions. \end{abstract}