Metallic islands in the Kondo insulator SmB6

J C Souza,P A Venegas,P F S Rosa,R R Urbano,M Carlone,P G Pagliuso,M O Malcolms,P M Menegasso,J Sichelschmidt,Z Fisk

doi:10.1103/physrevresearch.2.043181

Abstract

The authors study the effects of magnetic impurities in a Kondo insulator and demonstrate that the Kondo insulating state is destroyed locally around impurities.

Highlights

The Kondo insulator SmB6 has attracted a lot of interest for almost half a century due to numerous puzzling properties such as the physics of the hybridization gap, the mixed-valence ground state, nonzero specific heat at low temperatures, the crystalline electrical field ground state, and the saturation in the resistivity under T ≈ 4 K [1]
It is important to notice that all samples show a similar gap in the resistivity, which agrees with previous Corbino disk measurements and the effects of Sm vacancies on the resistivity of SmB6 [15]
Based on previous theoretical reports [24], we propose that when there is quantum interference between such metallic islands, due to the increase of Gd3+ concentration, effectively, the islands grow in size and, as a consequence, the carriers will have mobility to enable metallic properties in the electron spin resonance (ESR) line shape and ESR line parameters, which will lead to a local effect and will not reflect in the global properties of the system, such as dc resistivity

Summary

Introduction

The Kondo insulator SmB6 has attracted a lot of interest for almost half a century due to numerous puzzling properties such as the physics of the hybridization gap, the mixed-valence ground state, nonzero specific heat at low temperatures, the crystalline electrical field ground state, and the saturation in the resistivity under T ≈ 4 K [1]. The interest was renewed following the prediction that SmB6 is a topological Kondo insulator (TKI) [2,3]. Many experimental results support a TKI phase [4,5,6,7,8,9,10], but this classification remains a matter of contention [11]. Conflicting experimental results for SmB6 further complicate classification schemes. A bulk-activated insulating behavior is obtained in dc electrical resistance measurements [15], while ac conductivity measurements show localized states with conductivities orders of magnitude higher than the dc measurements [16,17,18]

Methods

Results

Conclusion