Nb-ti alloy superconductor has been widely used in thousands of known superconductors because of its excellent comprehensive properties. 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 multi-element transition group metal elements, it was found that the alloy showed unusually stable superconductivity under ultra-high pressure (pressure over one million atmospheres is ultra-high pressure, and 1 million atmospheres =100 GPa). Since niobium and titanium are the main components of this high entropy alloy, the research on the superconductivity of niobium and titanium alloy under ultra-high pressure can deepen the understanding of the microscopic mechanism of superconductivity of high entropy alloy.
Recently, the superconductivity of niob-ti alloy superconductors under ultra-high pressure has been systematically studied by the state key laboratory of superconductivity, institute of physics, Chinese academy of sciences/national research center for condensed matter physics, Beijing. It is found that niob-ti alloy maintains zero resistance superconductivity under pressure up to 261.7GPa, which indicates that niob-ti alloy is the most pressure-resistant superconductor known among all superconductors. This pressure is the highest pressure reported for superconductivity. Under this pressure, the transition temperature of the superconductor of niob-titanium alloy increased from 9.6k at normal pressure to 19.1k. The experimental results of high voltage reluctance of strong magnetic field showed that the critical magnetic field increased from 15.4t to 19T at pressure of 211GPa and temperature of 1.8k. This is the highest superconducting transition temperature and the highest critical magnetic field found in the transition group metal element alloy superconductor. There was no change in crystal structure at 200 GPa pressure, but the volume was compressed by about 43%.
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. The results are published in the journal science.
In addition, in terms of experimental technology, this study successfully combined the experiments on large scientific devices such as extreme high pressure conditions, strong magnetic field and synchrotron radiation, providing a new example for China to use its own large scientific devices to jointly carry out cutting-edge scientific research.
