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

W. T. Fuhrman; P. Nikolic

doi:10.1103/PhysRevB.90.195144

paper

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

arXiv:1409.3220 · doi:10.1103/PhysRevB.90.195144

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.

arXiv comment14 pages, 7 figures

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

Abstract

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