Creating superconductivity in WB2 through pressure-induced metastable planar defects

High-pressure electrical resistivity measurements reveal that the mechanical deformation of ultra-hard WB2 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 MgB2 (hP3, space group 191, prototype AlB2). Synchrotron x-ray diffraction measurements up to 145GPa show that the ambient pressure hP12 structure (space group 194, prototype WB2) 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.

Automated summary

High-pressure electrical resistivity measurements and theoretical calculations reveal that superconductivity can be induced in ultra-hard WB2 during compression, originating from the formation of metastable stacking faults and twin boundaries. The appearance of superconductivity is not accompanied by a structural transition, but instead correlated with the formation and percolation of mechanically-induced stacking faults and twin boundaries, as confirmed by synchrotron x-ray diffraction measurements.