Investigation of Surface State of Topological Kondo Insulator with Rashba Impurities

TL;DR

This study explores the surface states of topological Kondo insulators with Rashba impurities, revealing how magnetic impurities induce gaps in surface states and lead to unconventional plasmons, while bulk properties remain unaffected.

Contribution

It introduces a mean-field slave-boson approach to analyze surface state modifications due to magnetic impurities and Rashba effects in topological Kondo insulators, highlighting new plasmon phenomena.

Findings

Magnetic impurities open a gap at the Dirac surface states.

Rashba impurities do not impair Kondo screening or shift the quantum critical point.

Gapless Dirac spectrum supports spin plasmons with q^{1/2} dependence.

Abstract

We study a generic topological Kondo insulator system by performing a mean-field theoretic calculation within the frame-work of slave-boson protocol. We assume infinite Hubbard-type interaction among the localized electrons. The difference between the bulk metallic and insulating phases of the insulator is in the sign of nearest neighbor hopping of localized electrons. The hopping amplitude is positive for the metallic and negative for the insulating phase. The surface metallicity together with bulk insulation, however, requires very strong f electron localization. Furthermore, we find that the exchange field, arising due to the presence of the magnetic impurities on the surface of the system, opens a gap at the gapless Dirac dispersion of the surface states. For the gapped surface state spectrum, we find the possibility of intra-band as well as inter-band unconventional plasmons. The paramountcy of the bulk metallicity, and, in the presence of the Rashba impurities, the insulator surface comprising of helical liquids are the important outcomes of the present communication. The access to the gapless Dirac spectrum leads to spin plasmons with the usual wave vector dependence q^1/2. The Rashba coupling does not impair the Kondo screening and does not affect the quantum critical point for the bulk.