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.

*This work was supported by the US Department of Energy Basic Energy Sciences under Contract No. DE-SC-0020385. High pressure equipment development at University of Florida was supported by the National Science Foundation CAREER award DMR-1453752. The beamtime was made possible by the Chicago/DOE Alliance Center (CDAC), which is supported by DOE-NNSA (DE-NA0003975).

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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