In 1911, Dutch physicist Heike Kamerlingh Onnes discovered superconductivity for the first time by cooling mercury with liquid helium. After more than 100 years, scientists have worked tirelessly to explore superconductivity, including Five Nobel Prizes and ten Nobel Laureates.
New superconducting materials are constantly being discovered, each of which may reveal unprecedented research directions and possibilities. In 2018, Dr. Ding Zhang, an associate professor from the Department of Physics of Tsinghua University, opened up a "new world" in the field of two-dimensional superconductivity. His team discovered a new type of two-dimensional superconducting materials: ultrathin gray tin films. Afterward, Zhang Ding led the research team to carry out further ultra-low temperature electrical and magneto transport measurements of the ultrathin gray tin films, ranging from single layer to multilayer (a thickness of one to five atomic layers), and successfully demonstrated its superconductivity.
In order to further understand this two-dimensional superconductivity, Ding led his research team to collaborate with Dr. Joseph Falson and Professor Jurgen Smet of Max Planck Institute at Stuttgart. They used extremely low temperature and strong magnetic fields with the in-situ rotating measurement technology to obtain the critical magnetic field behavior of the superconductor samples with different thicknesses in almost the entire superconducting temperature range.
They found that the superconductivity of gray tin thin films can be resilient to a strong magnetic field, up to a value that far exceeds the upper limit set by the standard theory. At ultralow temperatures, the critical magnetic field gets even further enhanced, in sharp contrast to the conventional behavior. Based on this finding and by collaborating with theorists, they proposed a new mechanism for the enhanced critical magnetic field, outlining a general framework that greatly facilitates the search of superconductors with similar properties in a large material pool.
Regarding the future direction and work, Ding believes that gray tin thin films are still far from application and are not a material with very high superconducting temperatures. However, its advantage is that it is relatively stable in the air, and its superconductivity is relatively stable. The combination of topological properties will produce certain benefits for further experimental operations, such as quantum manipulation, but the premise is to prove that its topological properties and superconducting properties can indeed be combined to form topological superconductivity.