Coexistence of Surface Superconducting and Three-Dimensional Topological Dirac States in Semimetal KZnBi
Junseong Song, Sunghun Kim, Youngkuk Kim, Huixia Fu, Jahyun Koo, Zhen Wang, Gyubin Lee, Jouhahn Lee, Sang Ho Oh, Joonho Bang, Taku Matsushita, Nobuo Wada, Hiroki Ikegami, Jonathan D. Denlinger, Young Hee Lee, Binghai Yan, Yeongkwan Kim, Sung Wng Kim
Abstract
We report the discovery of a new three-dimensional (3D) topological Dirac semimetal (TDS) material KZnBi, coexisting with a naturally formed superconducting state on the surface under ambient pressure. Using photoemission spectroscopy together with first-principles calculations, a 3D Dirac state with linear band dispersion is identified. The characteristic features of massless Dirac fermions are also confirmed by magnetotransport measurements, exhibiting an extremely small cyclotron mass of m 0.012 m 0 and a high Fermi velocity of v F 1.04 10 6 m=s. Interestingly, superconductivity occurs below 0.85 K on the (001) surface, while the bulk remains nonsuperconducting. The captured linear temperature dependence of the upper critical field suggests the possible non-s-wave character of this surface superconductivity. Our discovery serves a distinctive platform to study the interplay between 3D TDS and the superconductivity.