Junseong Song1,Sunghun Kim2,Youngkuk Kim3,Young Hee Lee1,Binghai Yan4,Yeongkwan Kim2,Sung Wng Kim5
Center for Integrated Nanostructure Physics, Institute for Basic Science1,Department of Physics, Korea Advanced Institute of Science and Technology2,Department of Physics, Sungkyunkwan University3,Department of Condensed Matter Physics, Weizmann Institute of Science4,Department of Energy Science, Sungkyunkwan University5
Junseong Song1,Sunghun Kim2,Youngkuk Kim3,Young Hee Lee1,Binghai Yan4,Yeongkwan Kim2,Sung Wng Kim5
Center for Integrated Nanostructure Physics, Institute for Basic Science1,Department of Physics, Korea Advanced Institute of Science and Technology2,Department of Physics, Sungkyunkwan University3,Department of Condensed Matter Physics, Weizmann Institute of Science4,Department of Energy Science, Sungkyunkwan University5
Topological matters with superconducting state provide an exotic platform for realizing Majorana fermions that promise the building block of a quantum computation. Here 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 <i>m</i><sup>*</sup> = 0.012 <i>m</i><sub>0</sub> and a high Fermi velocity of <i>v</i><sub>F</sub> = 1.04 × 10<sup>6</sup> 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-<i>s</i>-wave character of this surface superconductivity. Our discovery serves a distinctive platform to study the interplay between 3D TDS and the superconductivity.<br/><br/>[ref] Junseong Song et al., Coexistence of surface superconducting and three-dimensional topological Dirac states in semimetal KZnBi. <i>Physical Review X</i> <b>11</b>, 021065 (2021)