Niobium titanium alloy superconductors have been widely used in thousands of known superconductors due to their excellent comprehensive properties and are the key materials in superconducting magnets for medical NMR and large scientific devices. Niobium titanium alloy is a typical binary alloy composed of transition group elements. In the previous study on the high entropy alloy superconductor (TaNb)0.67(HfZrTi)0.33 composed of multiple transition metal elements, it was found that the alloy exhibited exceptionally stable superconductivity under ultra-high pressure (the pressure above one million atmospheres is ultra-high pressure, 1 million atmospheres =100 GPa). Since niobium and titanium are the main elements of the high entropy alloy, the understanding of the microcosmic mechanism of superconductivity of the high entropy alloy can be enhanced by studying the superconductivity of niobium titanium alloy under ultra-high pressure.
The superconductivity of Nb-Ti alloy superconductor under ultra high pressure was studied systematically. It is found that Nb-Ti alloy maintains zero resistance at pressures up to 261.7GPa, which indicates that Nb-Ti alloy is the most pressure-resistant superconductor among all known superconductors. This pressure is the highest reported for superconductivity. The transition temperature of Nb Ti alloy superconductor increases from 9.6K to 19.1K at normal pressure, and the critical magnetic field increases from 15.4T to 19T at 211GPa and 1.8K at high pressure and temperature in Hefei. This is the highest superconducting transition temperature and the highest critical magnetic field ever found in a transition metal elemental alloy superconductor.
The study reveals the made of the element of transition metal alloy superconductor in high pressure the superconductivity can resist deformation and stability of characteristics, it has to do with copper oxides and iron-based superconductors superconductivity sensitivity to the height of the volume change is in stark contrast, and after the transition metal elements also superconductors (valence electronic d in closed shells) of the superconducting transition temperature drop behavior are obviously different according to the volume compression.
In addition, in terms of experimental techniques, this study successfully combines experiments in large scientific facilities, such as high pressure extreme conditions, strong magnetic field and synchrotron radiation.
