Speaker
Ryotaro Arita
University Tokyo
Date＆Time
2022.08.16（Tue）PM 14:00
Location
Zoom Meeting ID：950 680 6742 Password：2022
https://zoom.us/j/9506806742?pwd=TzEzUitXOTI1akFMSWhsU0R0K2FwZz0
Reporter
Dr. Ryotaro ARITA got his Ph.D at department of physics, University Tokyo at 2000. After that, he is a Research Associate, Department of Physics, University of Tokyo at 2000, and research Fellow of the Alexander von Humboldt Foundation, Max-Planck Institute for Solid State Research at 2004. He is a research Scientist and then promoted as Senior Research Scientist, Condensed Matter Theory Lab., RIKEN since 2006. He is back to Department of Applied Physics, Univ. Tokyo as a Associate Professor. At 2018, he became a professor, Department of Applied Physics, Univ. Tokyo. He also received many Awards, namely, Mar 2006: JDZB Science Award, The Society of Friends of the Japanese-German Center Berlin; Mar 2011: Young Scientist Award of the Physical Society of Japan; Apr 2012: The Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science and Technology, The Young Scientists' Prize; October 2015: Ryogo Kubo Memorial Prize; 2018-2021: Highly Cited Researcher (Clarivate Analytics); Mar 2019: Journal of the Physical Society of Japan, Outstanding Referee.
Abstract
While superconducting transition temperature (Tc) is one of the critical quantities characterizing superconductors, its calculation from first principles has been a challenge in computational materials science. For conventional superconductors mediated by phonons, we must consider the mass enhancement effect and the retardation effect. To take account of these two effects, we must solve the Eliashberg equation self-consistently, taking account of the significant difference in the energy scale of electrons and phonons. While the numerical cost to solve the Eliashberg equation from first principles has been extremely expensive, we recently developed an efficient scheme based on the intermediate representation of the Green's function. On the other hand, due to the strong Coulomb repulsion, the gap function of unconventional superconductors is usually anisotropic and has sign changes in the Brillouin zone. To treat this anisotropy, we have to consider spatial fluctuations in correlated electron systems. One promising approach is the dynamical vertex approximation, a diagrammatic extension of the dynamical mean-field approximation. In this talk, our recent calculations of Tc for conventional superconductors such as elemental metals and hydrides and that for unconventional superconductors such as Ni- and Pd-based superconductors will be discussed.
