Fluctuation of Chern Numbers in a Parametric Random Matrix Model

TL;DR

This paper studies how Chern numbers fluctuate in a parametric random matrix model, revealing short-range correlations of Weyl points and the scaling behavior of Chern number fluctuations with system size.

Contribution

It extends the analysis of a random matrix model to characterize the statistics and correlations of Weyl points and Chern number fluctuations in topological semimetals.

Findings

Weyl points with opposite polarities are short-range correlated.

Chern number fluctuation grows linearly before saturating.

Saturation value scales with the number of bands.

Abstract

Band-touching Weyl points in Weyl semimetals give rise to many novel characteristics, one of which the presence of surface Fermi-arc states that is topologically protected. The number of such states can be computed by the Chern numbers at different momentum slices, which fluctuates with changing momentum and depends on the distribution of Weyl points in the Brillouin zone. For realistic systems, it may be difficult to locate the momenta at which these Weyl points and Fermi-arc states appear. Therefore, we extend the analysis of a parametric random matrix model proposed by Walker and Wilkinson to find the statistics of their distributions. Our numerical data shows that Weyl points with opposite polarities are short range correlated, and the Chern number fluctuation only grows linearly for a limited momentum difference before it saturates. We also find that the saturation value scales with the total number of bands. We then compute the short-range correlation length from perturbation theory, and derive the dependence of the Chern number fluctuation on the momentum difference, showing that the saturation results from the short-range correlation.