Superconducting and normal-state anisotropy of the doped topological insulator Sr0.1Bi2Se3

M P Smylie; K Willa; H Claus; A E Koshelev; K W Song; W-K Kwok; Z Islam; G D Gu; J A Schneeloch; R D Zhong; U Welp

doi:10.1038/s41598-018-26032-0

Superconducting and normal-state anisotropy of the doped topological insulator Sr_0.1Bi₂Se₃

Sci Rep. 2018 May 16;8(1):7666. doi: 10.1038/s41598-018-26032-0.

Authors

M P Smylie^{1

2}, K Willa³, H Claus³, A E Koshelev³, K W Song³, W-K Kwok³, Z Islam⁴, G D Gu⁵, J A Schneeloch^{5

6}, R D Zhong^{5

7}, U Welp³

Affiliations

¹ Materials Science Division, Argonne National Laboratory, 9700 S. Cass Ave, Lemont, Illinois, 60439, USA. msmylie@anl.gov.
² Department of Physics, University of Notre Dame, Notre Dame, Indiana, 46556, USA. msmylie@anl.gov.
³ Materials Science Division, Argonne National Laboratory, 9700 S. Cass Ave, Lemont, Illinois, 60439, USA.
⁴ Advanced Photon Source, Argonne National Laboratory, 9700 S. Cass Ave, Lemont, Illinois, 60439, USA.
⁵ Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York, 11793, USA.
⁶ Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York, 11794, USA.
⁷ Department of Materials Science and Engineering, Stony Brook University, Stony Brook, New York, 11794, USA.

Abstract

Sr_xBi₂Se₃ and the related compounds Cu_xBi₂Se₃ and Nb_xBi₂Se₃ have attracted considerable interest, as these materials may be realizations of unconventional topological superconductors. Superconductivity with T_c ~3 K in Sr_xBi₂Se₃ arises upon intercalation of Sr into the layered topological insulator Bi₂Se₃. Here we elucidate the anisotropy of the normal and superconducting state of Sr_0.1Bi₂Se₃ with angular dependent magnetotransport and thermodynamic measurements. High resolution x-ray diffraction studies underline the high crystalline quality of the samples. We demonstrate that the normal state electronic and magnetic properties of Sr_0.1Bi₂Se₃ are isotropic in the basal plane while we observe a large two-fold in-plane anisotropy of the upper critical field in the superconducting state. Our results support the recently proposed odd-parity nematic state characterized by a nodal gap of Eu symmetry in Sr_xBi₂Se₃.