Seminar By Binghai Yan, Weizmann Institute of Science, Israel

Title: Spin, Orbital and Charge at Nonequilibrium Phase in Chirality-induced Spin Selectivity

Host: Peng Xiong

Abstract: The chirality-spin interaction is a fascinating topic for physicists and chemists. For example, chiral molecules like DNA generate giant spin polarization in nanodevices characterized by large magnetoresistance at room temperature. This phenomenon, called chirality-induced spin selectivity (CISS), paves a pathway for unconventional spintronic devices and enantiomer separation. Two basic questions emerge for CISS. What is the origin of the strong spin-orbit coupling (compared with room temperature) in organic molecules? Why is the CISS spin polarization so large (even larger than the ferromagnet contact)? The first question was recently clarified by an experiment [1] where the heavy-metal electrode contributes significant spin-orbit interaction. The second question refers to a more fundamental topic on the Onsager’s reciprocal relation [2]. Distinct from ordinary transport, CISS magnetoresistance violates Onsager's relation, and its physical mechanism remains elusive. In this talk, I will introduce our recent understanding on CISS and understand the chirality-driven phenomena in a unified framework [3]. We propose that the CISS magnetoresistance originates from the charge trapping that modifies the electron tunneling barrier and circumvents Onsager's reciprocity, which is indirectly related to spin. I will introduce more recent experiments [4,5] that verified some exotic predictions from this theory. Our work provides further insights to explore the magnetochiral interaction regarding spin, charge and chirality in chemical and biological interactions.

References:

[1] Y. Adhikari, T. Liu et al, Nature Comm, 14, 5163 (2023).

[2] B. Yan, Annu. Rev. Mater. Res. 54:97–115 (2024)

[3] J. Xiao, Y. Zhao, B. Yan, arXiv:2201.03623

[4] F. Wu et al. arXiv:2408.03501

[5] A. K. Singh et al. arXiv:2408.12258