Interaction Driven Subgap Spin Exciton in the Kondo Insulator SmB6

TL;DR

This paper investigates a coherent spin exciton in the topological Kondo insulator SmB6 using neutron scattering and theoretical modeling, revealing insights into its band structure and magnetic excitations.

Contribution

It presents the first detailed mapping of a subgap spin exciton in SmB6 and introduces a slave-boson model that explains its origin and relation to band inversion.

Findings

Identification of a 14 meV resonant mode confined to high symmetry points.

Dispersive behavior less than 2 meV consistent with a spin exciton.

Correlation between neutron scattering features and band inversion evidence.

Abstract

Using inelastic neutron scattering, we map a 14 meV coherent resonant mode in the topological Kondo insulator SmB6 and describe its relation to the low energy insulating band structure. The resonant intensity is confined to the X and R high symmetry points, repeating outside the first Brillouin zone and dispersing less than 2 meV, with a 5d-like magnetic form factor. We present a slave-boson treatment of the Anderson Hamiltonian with a third neighbor dominated hybridized band structure. This approach produces a spin exciton below the charge gap with features that are consistent with the observed neutron scattering. We find that maxima in the wave vector dependence of the inelastic neutron scattering indicate band inversion.