[Seminar] "Uniaxial-strain Control of Nematic Superconductivity in SrxBi2Se3" by Dr. Ivan Kostylev

Dr. Ivan Kostylev, Kyoto University

Title: Uniaxial-strain Control of Nematic Superconductivity in Sr_xBi₂Se₃

I. Kostylev¹, S. Yonezawa¹, Z. Wang^2,3, Y. Ando², Y. Maeno¹

¹ Department of Physics, Kyoto University, Kyoto 606-8502, Japan

²Institute of Physics II, University of Cologne, Köln 50937, Germany

³Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement, Ministry of Education (MOE), School of Physics, Beijing Institute of Technology, Beijing 100081, P. R. China

E-mail: kostylev@scphys.kyoto-u.ac.jp

Abstract:

Nematic states are characterized by rotational symmetry breaking without translational ordering. Recently, nematic superconductivity, in which the superconducting gap spontaneously lifts the rotational symmetry of the lattice, has been discovered [1-3]. In nematic superconductivity, multiple superconducting domains with different nematic orientations can exist, and these domains can be controlled by a conjugate external stimulus. Domain engineering are quite common in magnets but has not been achieved in superconductors. However, the pairing mechanism and the mechanism determining the nematic orientation remain unresolved.

A first step is to demonstrate control of the nematicity, through application of an external symmetry-breaking field, to determine the sign and strength of coupling to the lattice. Here, we report control of the nematic superconductivity and their domains of Sr_xBi₂Se₃, through in situ externally-applied uniaxial stress using a novel uniaxial strain cell (Fig. 1) [4, 5]. The suppression of subdomains indicates that it is the ∆_4y state that is most favored under compression along the basal Bi-Bi bonds. This fact allows us to determine the coupling parameter between the nematicity and lattice distortion.

These results provide an inevitable step towards microscopic understanding and future utilization of the unique topological nematic superconductivity [6].

[1] K. Matano et al., Nat. Phys. 12, 852 (2016).

[2] S. Yonezawa et al., Nat. Phys. 13, 123 (2017).

[3] S. Yonezawa, Condens. Matter 4, 2 (2019).

[4] I. Kostylev et al., J. Appl. Phys., 125, 082535 (2019).

[5] C. W. Hicks et al., Rev. Sci. Instrum. 85 (2014).

[6] I. Kostylev et al., arXiv: 1910.03252