Gauge-field fluctuations in 3D topological Mott insulators

TL;DR

This paper investigates the low-energy behavior of 3D topological Mott insulators, revealing a dimensional crossover in gauge field fluctuations that impacts surface spinons and leads to distinctive experimental signatures.

Contribution

It introduces a theoretical framework for understanding gauge-field fluctuations in 3D topological Mott insulators and describes a crossover from 3D to 2D behavior affecting surface states.

Findings

Gauge field fluctuations become effectively 2D in thin samples.

Heat capacity scales as T ln(1/T) due to gauge fluctuations.

Modified RKKY interactions are observed on the surface.

Abstract

We study the low-energy properties of three-dimensional (3D) topological Mott insulators which can be viewed as strong topological insulators of spinons interacting with a three-dimensional gauge field. The low-energy behavior of such systems is dominated by the two-dimensional (2D) gapless surface spinons coupled to the bulk gauge field. We find that a dimensional crossover from 3D to 2D in the gauge field fluctuations may occur as the systems thickness and/or temperature is varied. In the thin sample limit, the gauge field fluctuations effectively become 2D and the problem becomes analogous to the standard 2D spinon-gauge field theory. In the 3D limit, the bulk gauge field fluctuations lead to a low-energy theory for the coupled system that is more controlled than for the pure 2D case. We discuss various experimental signatures such as the heat capacity scaling as T ln 1/T as well as modified Ruderman-Kittel-Kasuya-Yoshida interactions on the surface.