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Suppression of superconducting transition temperature in MoB<sub>2</sub> via niobium substitution

ORAL

Abstract

Recently, superconductivity was discovered in diborides like MoB2 and WB2. It was found that MoB2, in an MgB2-like structure, superconducts at temperatures above 30 K near 100 GPa. Following these discoveries, we explored the high-pressure superconducting behavior of Nb-substituted MoB2 (Nb0.25Mo0.75B2). High pressure x-ray diffraction measurements revealed that Nb0.25Mo0.75B2 stays in P6/mmm structure to at least 160 GPa. Resistivity measurements showed a Tc of 8.15 K (confirmed by specific heat to be a bulk effect) at ambient pressure. The Tc is suppressed to ∼ 4 K at 50 GPa, before gradually rising to ∼ 5.5 K at 170 GPa. The critical temperature at high pressure in Nb0.25Mo0.75B2 is significantly lower than that found in MoB2 at high pressure (30 K), revealing that Nb-substitution results in a strong suppression of the superconducting critical temperature. The calculated Allen Dynes Tc at high pressure is significantly higher than the observed Tc. Possible explanations for these observations are discussed.

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Presenters

  • Shubham Sinha

    University of Florida

Authors

  • Shubham Sinha

    University of Florida

  • Jinhyuk Lim

    University of Florida

  • Ajinkya C Hire

    University of Florida

  • Jung S Kim

    University of Florida

  • Philip M Dee

    University of Florida

  • Ravhi Kumar

    University of Illinois at Chicago, University of Illinois Chicago, Department of Physics, University of Illinois Chicago, 845, W. Taylor Street, Chicago, IL 60607, University of Illinois, Chicago, Department of Physics, University of Illinois at Chicago

  • Dmitry Popov

    Argonne National Laboratory, HPCAT, X-ray Science Division, Argonne National Laboratory

  • Russell J Hemley

    University of Illinois at Chicago, University of Illinois Chicago, Departments of Physics, Chemistry, and Earth and Environmental Sciences, University of Illinois Chicago, Department of Physics and Chemistry, University of Illinois Chicago, 845, W. Taylor Street, Chicago, IL 60607, Departments of Physics, Chemistry, and Earth and Environmental Sciences, University of Illinois at Chicago

  • Richard G Hennig

    University of Florida

  • Peter Hirschfeld

    University of Florida

  • Gregory R Stewart

    University of Florida

  • James J Hamlin

    University of Florida, Dept. of Physics, University of Florida