Record-High Superconductivity in Niobium-Titanium Alloy.

ABSTRACT

The extraordinary superconductivity has been observed in a pressurized commercial niobium-titanium alloy. Its zero-resistance superconductivity persists from ambient pressure to the pressure as high as 261.7 GPa, a record-high pressure up to which a known superconducting state can continuously survive. Remarkably, at such an ultra-high pressure, although the ambient pressure volume is shrunk by 45% without structural phase transition, the superconducting transition temperature (TC ) increases to ≈19.1 K from ≈9.6 K, and the critical magnetic field (HC2 ) at 1.8 K has been enhanced to 19 T from 15.4 T. These results set new records for both the TC and the HC2 among all the known alloy superconductors composed of only transition metal elements. The remarkable high-pressure superconducting properties observed in the niobium-titanium alloy not only expand the knowledge on this important commercial superconductor but also are helpful for a better understanding on the superconducting mechanism.