Suppression of magnetic excitations near the surface of the topological Kondo insulator SmB6

TL;DR

This study investigates how magnetic excitations in the topological Kondo insulator SmB6 are suppressed near its surface, revealing a length scale of 40-90 nm related to excitonic states and their magnetic fluctuations.

Contribution

It provides detailed depth-dependent analysis of magnetic fluctuations in SmB6, linking suppression of spin excitons to surface proximity and identifying their spatial extent.

Findings

Magnetic field fluctuations are suppressed near the surface of SmB6.

Spin exciton fluctuations are reduced within 40-90 nm of the surface.

Surface proximity leads to a small increase in static magnetic fields.

Abstract

We present a detailed investigation of the temperature and depth dependence of the magnetic properties of 3D topological Kondo insulator SmB6 , in particular near its surface. We find that local magnetic field fluctuations detected in the bulk are suppressed rapidly with decreasing depths, disappearing almost completely at the surface. We attribute the magnetic excitations to spin excitons in bulk SmB6 , which produce local magnetic fields of about ~1.8 mT fluctuating on a time scale of ~60 ns. We find that the excitonic fluctuations are suppressed when approaching the surface on a length scale of 40-90 nm, accompanied by a small enhancement in static magnetic fields. We associate this length scale to the size of the excitonic state.