$\Gamma(2)$ modular symmetry, renormalization, group flow and the quantum Hall effect

TL;DR

This paper develops a family of holomorphic RG flow models with $ ext{Gamma}(2)$ modular symmetry that explains the stability of quantum Hall plateaus, reproduces the semi-circle law, and aligns qualitatively with experimental data.

Contribution

It introduces a novel class of $eta$-functions with modular symmetry that models quantum Hall transitions and reproduces key experimental phenomena.

Findings

RG flow preserves $ ext{Gamma}(2)$ symmetry

Semi-circle law derived from RG equations

Qualitative agreement with experimental conductivities

Abstract

We construct a family of holomorphic $\beta$-functions whose RG flow preserves the $\Gamma(2)$ modular symmetry and reproduces the observed stability of the Hall plateaus. The semi-circle law relating the longitudinal and Hall conductivities that has been observed experimentally is obtained from the integration of the RG equations for any permitted transition which can be identified from the selection rules encoded in the flow diagram. The generic scale dependance of the conductivities is found to agree qualitatively with the present experimental data. The existence of a crossing point occuring in the crossover of the permitted transitions is discussed.