Topological Dirac semimetals (TDSs) exhibit bulk Dirac cones protected by time reversal and crystal symmetry, as well as surface states originating from non-trivial topology. While there is a manifold possible onset of superconducting order in such systems, few observations of intrinsic superconductivity have so far been reported for TDSs. We observe evidence for a TDS phase in FeTe1−xSex (x = 0.45), one of the high transition temperature (Tc) iron-based superconductors. In angle-resolved photoelectron spectroscopy (ARPES) and transport experiments, we find spin-polarized states overlapping with the bulk states on the (001) surface, and linear magnetoresistance (MR) starting from 6 T. Combined, this strongly suggests the existence of a TDS phase, which is confirmed by theoretical calculations. In total, the topological electronic states in Fe(Te,Se) provide a promising high Tc platform to realize multiple topological superconducting phases.
@article{arxiv.1803.00845,
title = {Topological Dirac semimetal phase in the iron-based superconductor Fe(Te,Se)},
author = {Peng Zhang and Zhijun Wang and Yukiaki Ishida and Yoshimitsu Kohama and Xianxin Wu and Koichiro Yaji and Yue Sun and Cedric Bareille and Kenta Kuroda and Takeshi Kondo and Kozo Okazaki and Koichi Kindo and Kazuki Sumida and Shilong Wu and Koji Miyamoto and Taichi Okuda and Hong Ding and G. D. Gu and Tsuyoshi Tamegai and Ronny Thomale and Takuto Kawakami and Masatoshi Sato and Shik Shin},
journal= {arXiv preprint arXiv:1803.00845},
year = {2019}
}