In-gap collective mode spectrum of the Topological Kondo Insulator SmB6

Abstract

Samarium hexaboride (SmB${}_6$) is the first strongly correlated material with a recognized non-trivial band-structure topology. Its electron correlations are seen by inelastic neutron scattering as a coherent collective excitation at the energy of 14 meV. Here we calculate the spectrum of this mode using a perturbative slave boson method. Our starting point is the recently constructed Anderson model that properly captures the band-structure topology of SmB${}_6$. Most self-consistent renormalization effects are captured by a few phenomenological parameters whose values are fitted to match the calculated and experimentally measured mode spectrum in the first Brillouin zone. A simple band-structure of low-energy quasiparticles in SmB${}_6$ is also modeled through this fitting procedure, because the important renormalization effects due to Coulomb interactions are hard to calculate by ab-initio methods. Despite involving uncontrolled approximations, the slave boson calculation is capable of producing a fairly good quantitative match of the energy spectrum, and a qualitative match of the spectral weight throughout the first Brillouin zone. We find that the "fitted" band-structure required for this match indeed puts SmB${}_6$ in the class of strong topological insulators. Our analysis thus provides a detailed physical picture of how the SmB${}_6$ band topology arises from strong electron interactions, and paints the collective mode as magnetically active exciton.

14 pages, 7 figures

References in corpus (5)

• Discovery (theoretical prediction and experimental observation) of a large-gap topological-insulator class with spin-polarized single-Dirac-cone on the surface
• A topological Dirac insulator in a quantum spin Hall phase : Experimental observation of first strong topological insulator
• Correlated Topological Insulators with Mixed Valence
• Hybridization, Inter-Ion Correlation, and Surface States in the Kondo Insulator SmB6
• Surface Theory of a Family of Topological Kondo Insulators

Cited by in corpus (6)

• Interaction Driven Subgap Spin Exciton in the Kondo Insulator SmB6
• Excitons in topological Kondo insulators - theory of thermodynamic and transport anomalies in SmB${}_6$
• Anomalous 3D bulk AC conduction within the Kondo gap of SmB${}_6$ single crystals
• Universal spin wave damping in magnetic Weyl semimetals
• Collective modes in a Dirac insulator with short range interactions
• Screened moments in a Kondo insulator