Renormalization group approach to energy level statistics at the integer quantum Hall transition

TL;DR

This paper extends the real-space renormalization group method to analyze energy level statistics at the integer quantum Hall transition, successfully extracting the critical level spacing distribution and critical exponent with high accuracy.

Contribution

It introduces a novel RG approach analyzing phase distributions to determine the critical level spacing distribution and exponent at the quantum Hall transition.

Findings

The critical level spacing distribution is close but distinct from large-scale simulation results.

Away from the transition, the LSD approaches the Poisson distribution.

The critical exponent =2.37a0b1a00.02 matches established values.

Abstract

We extend the real-space renormalization group (RG) approach to the study of the energy level statistics at the integer quantum Hall (QH) transition. Previously it was demonstrated that the RG approach reproduces the critical distribution of the {\em power} transmission coefficients, i.e., two-terminal conductances, $P_{\text c}(G)$, with very high accuracy. The RG flow of $P(G)$ at energies away from the transition yielded the value of the critical exponent, $\nu$, that agreed with most accurate large-size lattice simulations. To obtain the information about the level statistics from the RG approach, we analyze the evolution of the distribution of {\em phases} of the {\em amplitude} transmission coefficient upon a step of the RG transformation. From the fixed point of this transformation we extract the critical level spacing distribution (LSD). This distribution is close, but distinctively different from the earlier large-scale simulations. We find that away from the transition the LSD crosses over towards the Poisson distribution. Studying the change of the LSD around the QH transition, we check that it indeed obeys scaling behavior. This enables us to use the alternative approach to extracting the critical exponent, based on the LSD, and to find $\nu=2.37\pm0.02$ very close to the value established in the literature. This provides additional evidence for the surprising fact that a small RG unit, containing only five nodes, accurately captures most of the correlations responsible for the localization-delocalization transition.