Creating superconductivity in WB2 through pressure-induced metastable planar defects
Jinhyuk Lim, Ajinkya C. Hire, Yundi Quan, J. S. Kim, Stephen Xie, Shubham Sinha, Ravhi S. Kumar, Dmitry Popov, Changyong Park, Russell J. Hemley, Yogesh K. Vohra, J. J. Hamlin, Richard G. Hennig, P. J. Hirschfeld, G. R. Stewart
Abstract
Abstract High-pressure electrical resistivity measurements reveal that the mechanical deformation of ultra-hard WB 2 during compression induces superconductivity above 50 GPa with a maximum superconducting critical temperature, T c of 17 K at 91 GPa. Upon further compression up to 187 GPa, the T c gradually decreases. Theoretical calculations show that electron-phonon mediated superconductivity originates from the formation of metastable stacking faults and twin boundaries that exhibit a local structure resembling MgB 2 (hP3, space group 191, prototype AlB 2 ). Synchrotron x-ray diffraction measurements up to 145 GPa show that the ambient pressure hP12 structure (space group 194, prototype WB 2 ) continues to persist to this pressure, consistent with the formation of the planar defects above 50 GPa. The abrupt appearance of superconductivity under pressure does not coincide with a structural transition but instead with the formation and percolation of mechanically-induced stacking faults and twin boundaries. The results identify an alternate route for designing superconducting materials.