Ground state anomalies in SmB6

Anup Pradhan Sakhya,Kalobaran Maiti

doi:10.1038/s41598-020-58172-7

Anup Pradhan Sakhya, Kalobaran Maiti

Open Access

https://doi.org/10.1038/s41598-020-58172-7

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Journal: Scientific Reports	Publication Date: Jan 27, 2020
Citations: 11	License type: open-access

Affiliation: Tata Institute of Fundamental Research

Abstract

SmB6 has drawn much attention in recent times due to the discovery of anomalies in its ground state properties as well as prediction of topologically protected gapless surface states. Varied theories have been proposed to capture the ground state anomalies. Here, we studied the electronic structure of SmB6 employing density functional theory using different exchange correlation potentials, spin-orbit coupling and electron correlation strength. We discover that a suitable choice of interaction parameters such as spin-orbit coupling, electron correlation strength and exchange interaction within the generalized gradient approximation provides a good description of the spectral functions observed in the angle-resolved photoemission spectroscopy (ARPES) studies. The Fermi surface plots exhibit electron pockets around X-point and hole pockets around ΓX line having dominant Sm 4f character. These observations corroborate well with the recent experimental results involving quantum oscillation measurements, ARPES, etc. In addition to primarily Sm 4f contributions observed at the Fermi level, the results exhibit significantly large contribution from B 2p states compared to weak Sm 5d contributions. This suggests important role of B 2p - Sm 4f hybridization in the exotic physics of this system.

Highlights

SmB6 has drawn much attention in recent times due to the discovery of anomalies in its ground state properties as well as prediction of topologically protected gapless surface states
It is evident that the energy distribution of the Sm 4f contributions look similar to B 2p contributions, which is a signature of hybridization between Sm 4f - B 2p states
We find that Sm 4f multiplets calculated using generalized gradient approximation (GGA) + spin orbit coupling (SOC) + U scheme provide a good description of the experimental angle-resolved photoemission spectroscopy (ARPES) data for the electron correlation strength of 7 eV and exchange interaction strength of 0.83 eV

Summary

Introduction

SmB6 has drawn much attention in recent times due to the discovery of anomalies in its ground state properties as well as prediction of topologically protected gapless surface states. The Fermi surface plots exhibit electron pockets around X-point and hole pockets around ΓX line having dominant Sm 4f character These observations corroborate well with the recent experimental results involving quantum oscillation measurements, ARPES, etc. In addition to primarily Sm 4f contributions observed at the Fermi level, the results exhibit significantly large contribution from B 2p states compared to weak Sm 5d contributions This suggests important role of B 2p - Sm 4f hybridization in the exotic physics of this system. Employing spin-resolved ARPES measurements, Xu et al.[17] showed that the metallic surface states in this material are spin polarized and the spin texture fulfills the condition that the surface states are protected by time-reversal symmetry suggesting SmB6 to be an example of a topological Kondo insulator. Quantum oscillation experiments by Li et al exhibit signature of two dimensional Fermi surfaces on (100) and (101) surface planes supporting the presence of topological surface states within the bulk hybridization gap[18]

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Conclusion