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►【“凝聚态物理-中关村论坛”第426期讲座】

报告题目：Chiral metals and superconductors for novel spintronics

报 告 人： Prof. Dr. Hiroshi Yamamoto
                  Institute for Molecular Science

报告时间：2024年2月28日（星期三）上午10：00

报告地点：线上/中国科学院物理研究所M楼253报告厅 

报告摘要： 

Hiroshi Yamamoto received his D. Sc. degree in solid state chemistry at University of Tokyo in 1998. After one year service as an assistant professor at Department of Physics, Gakushuin University, he spent 13 years as a research scientist at RIKEN. Since 2012, he serves as a full professor at Institute for Molecular Science, National Institutes of Natural Sciences in Japan. His research interests focus on organic electronics and spintronics based on novel operation mechanism. More specifically, an organic superconductor transistor and spintronic devices based on chirality are two major current topics in his study.

报告人简介：

Chirality-Induced Spin Selectivity (CISS) is attracting recent attention as a new source of spin polarized current. It also provides unique methods for enantio-separation, enantio-selective electrochemical reactions, and an efficient water oxidation. The mechanism of CISS effect is, however, yet to be clarified, as the effect is much larger than expected one estimated with small spin-orbit coupling for organic molecules. In a hypothetical consideration, it is proposed that an enhancement of spin polarization is associated with anti-parallel spin polarizations at two opposite ends of a chiral molecule created. It is interesting to note that such an anti-parallel spin pair is time-reversal (T) odd state, while the chiral molecular structure is T-even. We think symmetry conversion from T-even to T-odd quantities gives an essential clue to understand CISS effect that can generate huge spin polarization in a non-equilibrium condition.
We have made such a symmetry consideration based on multipole basis and found that a T-odd chirality can emerge from an accumulation of spin current (= electrical toroidal monopole) at reservoirs. In a chiral metal, we have confirmed that the CISS effect appears as spin polarizing rather than spin filtering. In addition, we have shown that chiral organic superconductor can exhibit spin accumulation at two opposite crystal edges whose directions are anti-parallel to one another. This can be regarded as a macroscopic-size emulation of chiral molecules that has T-odd spin accumulations at their opposite ends. A connection to falsely chiral influence will be also discussed.