Niobium titanium alloy is currently the most pressure-resistant superconductor

Recently, the State Key Laboratory of Superconductivity, Institute of Physics, Chinese Academy of Sciences/Beijing National Research Center for Condensed Matter Physics, and Princeton University have conducted a systematic study on the superconductivity of niobium-titanium alloy superconductors under ultra-high pressure. It is found that niobium titanium alloy still maintains zero resistance superconductivity at pressures up to 261.7GPa, indicating that niobium titanium alloy is the most pressure-resistant superconductor known to date. This pressure is the highest pressure at which superconductivity has been reported. Under this pressure, the superconducting transition temperature of niobium titanium alloy superconductor increases from 9.6K to 19.1K, and the experimental results of Hefei high magnetic field high pressure reluctance show that its critical magnetic field increases from 15.4T to 19T at 211GPa pressure and 1.8K temperature. This is the highest superconducting transition temperature and the highest critical magnetic field found in superconductors of transition metallic elements alloy. The results of high pressure SYNchrotron X-ray diffraction (XRD) experiments of Shanghai light Source show that the crystal structure does not change at 200 GPa, but its volume is reduced by about 43%.

Niobium titanium alloy superconductor has been widely used in thousands of known superconductors for its excellent comprehensive performance. It is the key material in medical nuclear magnetic resonance and large scientific device superconducting magnet. Niobium titanium alloy is a typical binary alloy composed of transition group elements. In the previous study, it was found that the high entropy alloy superconductor (TaNb)0.67(HfZrTi)0.33, which is composed of multiple transition metal elements, exhibits unusually stable superconductivity under ultra-high pressure (pressure above 1 million atmospheres is ultra-high pressure, 1 million atmospheres =100 GPa). Since niobium and titanium are the main components of the high entropy alloy, the study of the superconductivity of niobium titanium alloy under ultra-high pressure can deepen the understanding of the microscopic mechanism of high entropy alloy superconductivity.

These studies reveal that the superconductivity of alloy superconductors composed of transition metal elements can withstand large deformation and exist stably under high pressure, which is in sharp contrast to the high sensitivity of superconductivity of copper oxide and iron based superconductors to volume changes. It is also different from the superconducting transition temperature of post-transition metallic element superconductors (full shell of d electrons in valence electrons) that decreases with volume compression. In this study, experiments on high pressure extreme conditions, high magnetic field and synchrotron radiation were successfully combined, providing a new example for China to jointly carry out frontier scientific research with its own large scientific equipment.