セミナー案内

日時
2月 4日 (水), 14:00-
場所
Onsite (Room 413)
お問い合わせの際はtanaka.hiroto.54z[@]st.kyoto-u.ac.jp ([]を外す) までご連絡ください。
講演者
Mr. Shun Asano (Condensed Matter Theory Group)
タイトル
"Chirality-induced spin-selective Peierls transition "
備考欄　（アブストラクト等）

Abstract:
 Chirality is a ubiquitous concept in wider range of science. Recent vibrant research has revealed many fascinating phenomena reflecting structural chirality, e.g., optical activity and chirality induced spin selectivity (CISS) [1]. Simultaneously, some attempts have been made to obtain a desirable chiral structure from an achiral crystal by some external means through electrons, molecules, and so on [2]. For instance, structural chirality has been revealed to arise by breaking the compensation of phonon handedness, which are inherently degenerate in the original achiral phase.
 The structural chirality affects their electrons and vice versa, which have been demonstrated independently so far. Then, does the cooperation between structural chirality and its constituents trigger unique phenomena? In usual crystals, Peierls transition (PT) exemplifies the cooperative phenomena by the electrons and the structure, i.e., phonons. The features of PT encompass both of them, which involve fascinating phenomena. Thus, PT in chiral materials with both prominent structure and exotic conductivity, can be expected to trigger a novel phase. Nevertheless, the exploration about chirality in PT is limited to the context of achiral-chiral phase transitions [3], and accordingly the above question remains to be unveiled.
 We here investigate PT in the case where parent phase is chiral with screw symmetry and, predict a novel phase transition, chirality induced spin selective Peierls transition (CISSPT). We discuss the Kohn anomaly of chiral phonons, which reveal the nesting vector encompasses the information of both momentum and angular momentum. This unconventional Kohn anomaly induces spin selective Peierls gap to electron system [4]. In CISSPT, electrons obtain helical spin density wave order and additional helical lattice distortion is induced into crystals.

References:
[1] B. P. Bloom et al., Chem. Rev. 124, 1950 (2024).
[2] Z. Zeng et al., Science 387, 431 (2025).
[3] K. Luo and X. Dai, Phys. Rev. X 13, 011027 (2023).
[4] B. Braunecker et al., Phys. Rev. B 82, 045127 (2010).