CuxBi2Se3 hosts both topological surface states and bulk superconductivity. It has been identified recently as a topological superconductor (TSC) with an extraordinary nematic, i. e. C2-symmetric, superconducting state and odd-parity pairing. Here, using scanning tunneling microscopy (STM), we directly examine the response of the superconductivity of CuxBi2Se3 to magnetic field. Under out-of-plane fields, we discover elongated magnetic vortices hosting zero-bias conductance peaks consistent with the Majorana bound states expected in a TSC. Under in-plane fields, the average superconducting gap exhibits two-fold symmetry with field orientation; the long C2 symmetry axes are pinned to the dihedral mirror planes under B//=0.5 T but rotate slightly under B//=1.0 T. Moreover, a nodeless {\Delta}4x gap structure is semi-quantitatively determined for the first time. Our data paint a microscopic picture of the nematic superconductivity in CuxBi2Se3 and pose strong constraints on theory.
@article{arxiv.1804.09122,
title = {Direct visualization of the nematic superconductivity in Cu$_x$Bi$_2$Se$_3$},
author = {Ran Tao and Ya-Jun Yan and Xi Liu and Zhi-Wei Wang and Yoichi Ando and Qiang-Hua Wang and Tong Zhang and Dong-Lai Feng},
journal= {arXiv preprint arXiv:1804.09122},
year = {2019}
}
Comments
14 pages, 4 figures; reference added, text and figures modified