Semiclassical Approach to Parametric Spectral Correlation with Spin 1/2

TL;DR

This paper develops a semiclassical method using Brownian motion on a sphere to analyze parametric spectral correlations in chaotic systems with spin 1/2, aligning with GSE predictions and describing transitions between spectral universality classes.

Contribution

It introduces a novel semiclassical approach employing Brownian motion on a sphere to model parametric spectral correlations and transitions between GSE and GOE universality classes.

Findings

The small time expansion of the form factor matches parametric random matrix theory predictions.

The method describes the transition from GOE to GSE as the spin effect increases.

The approach provides a semiclassical understanding of spectral correlations with spin 1/2.

Abstract

The spectral correlation of a chaotic system with spin 1/2 is universally described by the GSE (Gaussian Symplectic Ensemble) of random matrices in the semiclassical limit. In semiclassical theory, the spectral form factor is expressed in terms of the periodic orbits and the spin state is simulated by the uniform distribution on a sphere. In this paper, instead of the uniform distribution, we introduce Brownian motion on a sphere to yield the parametric motion of the energy levels. As a result, the small time expansion of the form factor is obtained and found to be in agreement with the prediction of parametric random matrices in the transition within the GSE universality class. Moreover, by starting the Brownian motion from a point distribution on the sphere, we gradually increase the effect of the spin and calculate the form factor describing the transition from the GOE (Gaussian Orthogonal Ensemble) class to the GSE class.