Steady-state high magnetic field experimental device (SHMFF) user Researcher Sun Liling's research group at the Institute of Physics, Chinese Academy of Sciences has made important progress in the research of superconductivity under extreme conditions of high magnetic field, ultrahigh pressure, and low temperature. The superconducting transition temperature and upper critical magnetic field are significantly increased. Related research results were published in Advanced Materials, the top academic journal of materials science.
Niobium-titanium alloys have been widely used in thousands of known superconductors for their excellent comprehensive properties, and are the key materials in current medical nuclear magnetic resonance and large scientific devices superconducting magnets. Sun Liling's research group found in a previous study on high-entropy alloy superconductors (TaNb) 0.67 (HfZrTi) 0.33 composed of multiple transition group metal elements. Atmospheric pressure = 100 GPa), the alloy shows exceptionally stable superconductivity. Since niobium and titanium are the main constituent elements of this high-entropy alloy, by studying the superconductivity of niobium-titanium alloy under ultra-high pressure, it is possible to deepen the understanding of the superconducting micro-mechanism of high-entropy alloy.
Recently, the research team of Sun Liling used SHMFF to systematically study the superconductivity of niobium-titanium alloy superconductors under ultra-high pressure. It was found that the niobium-titanium alloy still maintained superconductivity under a pressure of up to 261.7 GPa, which indicates that the niobium-titanium alloy is the most voltage-resistant superconductor among all superconductors currently known. At the same time, this pressure is the highest pressure that has been reported for superconductivity, under which the superconducting transition temperature of niobium-titanium alloy is increased from 9.6K to 19.1K at normal pressure. On this basis, the assistant researcher Guo Jing of Sun Liling's research group integrated the strong magnetic field (30 Tesla), ultra high voltage (261.7GPa), Low temperature (1.8K) comprehensive extreme conditions were systematically studied on the superconducting properties of niobium-titanium alloys under comprehensive extreme conditions. It was found that the upper critical magnetic field of the alloy superconductor under ultra-high pressure will have a significant increase, and its critical magnetic field increased from 15.4T to 19T at a temperature of 1.8K. The Shanghai Xunyuan synchrotron radiation high-pressure XRD experiment results show that the crystal structure of the niobium-titanium alloy has not changed under the pressure of 200GPa, but its volume has been compressed by about 43%. The above research reveals that the superconductivity of alloy superconductors composed of transition group metal elements can resist large deformation and stably exist under high pressure, which provides a wide application of niobium-titanium alloy and related materials in high-field superconducting magnets in accordance with.
In addition to its scientific significance, this work has technically achieved the highest international pressure indicators under the combined extreme conditions of strong magnetic fields, ultrahigh pressures, and low temperatures, and provides an advanced platform for exploring the physical properties under comprehensive extreme conditions in the future.