Quantum spin fluctuations in the bulk insulating state of pure and Fe-doped SmB6

TL;DR

This study investigates the quantum spin fluctuations in the bulk insulating state of pure and Fe-doped SmB6, revealing low-temperature magnetic excitations driven by quantum effects using muon spin techniques.

Contribution

It provides the first local magnetic measurements of Fe-doped SmB6, showing how Fe impurities influence bulk magnetism and quantum spin fluctuations in the insulating state.

Findings

Fe doping induces changes in bulk magnetism below 6 K

Quantum fluctuations drive low-lying magnetic excitations

Bulk magnetic relaxation rate is temperature-independent at low temperatures

Abstract

The intermediate-valence compound SmB6 is a well-known Kondo insulator, in which hybridization of itinerant 5d electrons with localized 4f electrons leads to a transition from metallic to insulating behavior at low temperatures. Recent studies suggest that SmB6 is a topological insulator, with topological metallic surface states emerging from a fully insulating hybridized bulk band structure. Here we locally probe the bulk magnetic properties of pure and 0.5 % Fe-doped SmB6 by muon spin rotation/relaxation methods. Below 6 K the Fe impurity induces simultaneous changes in the bulk local magnetism and the electrical conductivity. In the low-temperature insulating bulk state we observe a temperature-independent dynamic relaxation rate indicative of low-lying magnetic excitations driven primarily by quantum fluctuations.