10 марта в 13:30 состоится семинар лаборатории Теоретической электродинамики конденсированного состояния (под рук. д.ф.-м.н. А.Л. Рахманова) на тему "Нематическая сверхпроводимость в допированном топологическом изоляторе: эффект гексагональных искажений"

NEMATIC SUPERCONDUCTIVITY IN DOPED TOPOLOGICAL INSULATORS: EFFECT OF HEXAGONAL WARPING

A.L. Rakhmanov, R.S. Akzyanov, A.Yu. Kuntsevich3, and D.A. Khokhlov

There is a numerous experimental evidence for the nematic superconductivity with the Eu pairing in doped topological insulators. Recent experiments give a direct evidence for this in high-quality single crystals of doped SrxBi2Se3 [1]. It was observed that the upper critical magnetic field Hc2 has a twofold rotational symmetry and depends on the sign of the crystal strain: in the stretched samples the maximum of Hc2 is achieved when the in-plane field is transverse to the strain axis, while in the compressed samples this maximum is observed when the field is along the strain direction. This result is naturally explained within a framework of the odd-parity nematic superconductivity. However, from the first theoretical alert, the origin of the nematic superconductivity in the doped topological insulators is a mystery. In their seminal work [2], Fu and Berg show that the triplet superconducting order parameter with A1u representation is always favorable in comparison with the nematic Eu order. We study the superconducting properties of the bulk states of a doped topological insulator with taking into account the hexagonal warping of the Fermi surface that was ignored in [2]. We obtain that this effect stabilizes the observed nematic spin-triplet superconducting phase with Eu pairing. The nematic order parameter opens a full gap in the spectrum. This gap demonstrates a non-BCS behavior and strongly depends on doping.

References

1. 1. A.Yu. Kuntsevich, M.A. Bryzgalov, R.S. Akzyanov, V.P. Martovitskii, A.L. Rakhmanov, Yu.G. Selivanov, Strain-driven nematicity of the odd-parity superconductivity in SrxBi2Se3, Phys. Rev. B, 100, 224509 (2019)
2. 2. L. Fu and E. Berg, Odd-Parity Topological Superconductors: Theory and Application to CuxBi2Se3, Phys. Rev. Lett. 105, 097001 (2010)