A notable characteristic of PbTaSe2, a prototypical noncentrosymmetric (NCS) superconductor, is that its superconductivity can be modulated through a structural transition under hydrostatic pressure [Phys. Rev. B 95, 224508 (2017)]. Here we report on simultaneous pressure-sensitive point-contact Andreev reflection (PCAR) spectroscopy and bulk resistance measurements on PbTaSe2, to elucidate the nature of the surface and bulk superconductivity and their evolution with hydrostatic pressure. It is found that in high pressure region the superconducting gap opening temperature TcA is significantly lower that the bulk resistive transition temperature TcR, revealing a clear experimental signature of surface-bulk separation associated with enhanced antisymmetric spin-orbit coupling (ASOC). The PCAR spectra, reflecting the superconducting surface state, are analyzed with the Blonder-Tinkham-Klapwijk theory, yielding an isotropic s-wave full BCS-gap in the strong coupling regime. Analysis based on a modified McMillan formula indicates a sizable coupling strength contributed from ASOC for the superconducting surface state. These results suggest the coexistence of full gap s-wave superconductivity and topological surface states in PbTaSe2, indicating that this NSC with significantly enhanced ASOC may offer a solid platform to investigate the topological aspect in the superconducting condensate.
@article{arxiv.2103.07144,
title = {Topological Surface Superconductivity Induced by Hydrostatic Pressure-Enhanced Antisymmetric Spin-Orbit Coupling in Non-Centrosymmetric Superconductor PbTaSe2},
author = {Cong Ren and Hai Zi and Yu-jia Long and Lin-xiao Zhao and Xing-yuan Hou and Huan-xing Yang and Yi-feng Yang and Lei Shan and Zhi-an Ren and Jian-qi Li and Jiang-ping Hu and Peng Xiong and Geng-fu Chen},
journal= {arXiv preprint arXiv:2103.07144},
year = {2021}
}