1. breaking time-reversal symmetry and spin selection in chiral molecules

Amnon Aharony

School of Physics and Astronomy, Tel Aviv University, Israel

16 February 2021 Tue 4 pm

                                      IBS Center for Theoretical Physics of Complex Systems (PCS), Administrative Office (B349), Theory Wing, 3rd floor

                                      Expo-ro 55, Yuseong-gu, Daejeon, South Korea, 34126 Tel: +82-42-878-8633                     

Many recent experiments discovered chiral-induced spin selectivity (CISS): electrons scattered by helical organic molecules become spin-polarized. The theoretical explanation of this phenomenon is still under debate. Many theories start with spin-orbit interactions (SOIs) on the molecule, but the SOI preserves time-reversal symmetry, and therefore implies no spin selectivity in the linear conductance when the molecule connects two single channel terminals (Bardarson's theorem). Here we model the molecule by a tight-binding Hamiltonian, with a Rashba SOI along the helix and additional hopping in the direction of the helix axis, and present several ways to overcome the theorem and achieve CISS: allowing leakage from the molecular ions, adding a third terminal, adding magnetic fields, adding time-dependent potentials, adding more orbital states on the molecule, and various non-linear effects. [1] All of these yield CISS, so we are still far from having a unique explanation. Recent alternative theories will be criticized. [2]

[1] Many relevant references are included in Y. Utsumi, O. Entin-Wohlman, and A. Aharony, Spin selectivity through time-reversal symmetric helical junctions, Phys. Rev. B 102, 035445 (2020) - Editors' suggestion; (arXiv:2005.04041).

[2] O. Enrin-Wohlman, A. Aharony, and Y. Utsumi, Comment on: "Spin-orbit interaction and spin selectivity for tunneling electron transfer in DNA"
Accepted to appear in Phys. Rev. B;