A Strongly-Interacting Dirac Liquid on the Surface of a Topological Kondo Insulator

TL;DR

This paper investigates how Kondo fluctuations influence the topological surface states of a Kondo insulator, revealing strong interactions, spectrum renormalization, and potential magnetic instabilities beyond mean-field approximations.

Contribution

The study develops an effective theory incorporating Kondo fluctuations, showing their impact on surface state interactions and stability, advancing understanding beyond previous mean-field models.

Findings

Kondo fluctuations induce strong repulsive interactions among surface states.

Surface plasmon spectrum is significantly renormalized by these interactions.

Potential magnetic instability of the surface spectrum is suggested.

Abstract

A topological Kondo insulator (TKI) is a strongly-correlated material, where hybridization between the conduction electrons and localized f-electrons gives rise to a crossover from a metallic behavior at high temperatures to a topologically non-trivial insulating state at low temperatures. The existing description of the TKIs is based on a slave-boson mean-field theory, which neglects dynamic fluctuation phenomena. Here, we go beyond the mean-field theory and investigate the role of Kondo fluctuations on the topological surface states. We derive an effective theory of the Dirac surface states coupled to fluctuations and show that the latter mediate strong repulsive interactions between surface excitations. We show that these effects renormalize the plasmon spectrum on the surface. We also argue that Kondo-mediated interactions may drive a magnetic instability of the surface spectrum.