Abstract

Speaker: Prof Katsuya Shimizu, KYOKUGEN , Center for Science and Technology under Extreme Conditions, Graduate School of Engineering Science, Osaka University

Abstract: High pressure is one of the useful tools for studying material properties such as superconductivity. Not a few systems became superconductive under the combination of low temperature and high pressure. We have focused on simple elements for the candidate of superconductor and found that some elements exhibit relatively higher critical temperature, Tc at high pressure than at ambient. A lighter element is expected to show a higher Tc according to the conventional BCS theory. An example is hydrogen. The appearance of superconductivity at room temperature is predicted theoretically in the metallic phase [1]. However, experimental realization of metallic hydrogen has not yet been attained. The highest Tc in elements was found in compressed calcium [2] with 30 K at very high pressure exceeding 200 GPa. Recently, Tc > 200 K was reported in high-pressure phases of hydrides [3-5].

In my talk, the experimental investigations of pressure-induced superconductivity with our developments of high-pressure technique combined with low-temperature equipment will be reviewed. The recent results of the onset of new hydride superconductors will also be presented.

[1] C. F. Richardson, N. W. Ashcroft, Phys. Rev. Lett. 78, 118 (1997). [2] M. Sakata, et al., Phys. Rev. B 83 , 220512 (2011). [3] A. P. Drozdov, et al., Nature 525, 73 (2015). [4] A. P. Drozdov, et al., Nature 569, 528 (2019). [5] M. Somayazulu, et al., Phys. Rev. Lett. 122, 027001 (2019).

Biography: Professor Katsuya Shimizu is Professor at the Center for Science and Technology under Extreme Conditions, Osaka University, Japan. He received his PhD from Osaka University, Japan. His interests is condensed matter physics at extreme conditions, and especially superconductivity under pressure. He was awarded with the Van Valkenburg Award (1998), the Sir Martin Wood Prize (2000), the Nishina Memorial Prize (2001), the Prize for Superconducting Science and Technology (2002), Bernd T. Matthias Prize (20018).

E-mail: shimizu.katsuya.es@osaka-u.ac.jp

contact: Suchitra Sebastian (ses59@cam.ac.uk) or Siddharth Saxena (sss21@cam.ac.uk)