Two-gap superconductivity and topological surface states in TaOsSi

Xu, C. Q.; Li, B.; Feng, J. J.; Jiao, W. H.; Li, Y. K.; Liu, S. W.; Zhou, Y. X.; Sankar, R.; Zhigadlo, Nikolai D.; Wang, H. B.; Han, Z. D.; Qian, B.; Ye, W.; Zhou, W.; Shiroka, T.; Biswas, Pabitra K.; Xu, Xiaofeng; Shi, Z. X. (2019). Two-gap superconductivity and topological surface states in TaOsSi. Physical review. B - condensed matter and materials physics, 100(13) American Physical Society 10.1103/PhysRevB.100.134503

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The occurrence of superconductivity in topological materials is considered as a promising route for realizing topological superconductors, a platform able to host the long-sought Majorana fermions in condensed matter. In this work, by using electrical transport and heat-capacity measurements, as well as first-principles band-structure calculations, we investigate the physical properties of TaOsSi, a superconductor with Tc≈5.8 K. The behavior of both its upper critical field and low-temperature heat-capacity suggest the existence of two superconducting gaps. More strikingly, first-principles calculations reveal gapless topological surface states in the present material. The evolution of the electrical resistivity with pressure (up to 50 GPa) was also investigated, and a “V-shaped” diagram of Tc vs P was found. Overall, our data suggest that TaOsSi is a new system where multiband superconductivity and topological surface states coexist and, hence, it may serve as a possible candidate in the search for topological superconductivity.

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