An effect of Sm vacancies on the hybridization gap in topological Kondo insulator candidate SmB$_6$

TL;DR

This study investigates how Sm vacancies affect the hybridization gap in SmB$_6$, revealing that vacancies above 1% fill the gap with impurity states and increase low-temperature heat capacity, impacting its topological properties.

Contribution

It provides the first comparative analysis of how Sm vacancies influence the hybridization gap and low-temperature properties in SmB$_6$ using Raman and heat capacity measurements.

Findings

Hybridization gap is highly sensitive to Sm vacancies.

Vacancies above 1% fill the gap with impurity states.

Low-temperature heat capacity increases with vacancy concentration.

Abstract

A necessary element for the predicted topological state in Kondo insulator SmB$_6$ is the hybridization gap which opens in this compound at low temperatures. In this work, we present a comparative study of the in-gap density of states due to Sm vacancies by Raman scattering spectroscopy and heat capacity for samples where the number of Sm vacancies is equal to or below 1 %. We demonstrate that hybridization gap is very sensitive to the presence of Sm vacancies. At the amount of vacancies above 1 % the gap fills in with impurity states and low temperature heat capacity is enhanced.