Tunneling spin current in systems with spin degeneracy: Insights from geometric correction

by Yuta Suzuki (University of Tokyo)

Wednesday 12 Jul 2023, 11:00 → 12:15 Europe/Zurich

WBGB/019

When a strong electric field is applied to an insulator, electrons can tunnel through its band gap via non-adiabatic transitions. In the simplest case, this transition probability follows the Landau-Zener formula. Moreover, recent studies has revealed the presence of a geometric correction to the tunneling probability, which stems from the nature of the Bloch wavefunction [1, 2]. This geometric correction is characterized by a gauge invariant known as the shift vector, which is constructed from the Berry connections of two adjacent bands.

In this tallk, I will explore the incorporation of spin degrees of freedom into the tunneling process of Bloch electrons. I will present one of the mechanism for generating spin-polarized currents associated with tunneling in insulators, focusing on the connection with the aforementioned geometric correction [3]. This contribution becomes particularly prominent in PT-symmetric insulators, where each band is doubly degenerate with opposite spins but spin current component can be induced by a strong electric field. To illustrate this phenomenon, I will present a minimal model of an insulator with a zigzag chain structure, and demonstrate that its spin-dependent shift vector plays an essential role in the generation of spin current.

 

 [1] M. V. Berry, Proc. R. Soc. A 430, 405 (1990).

[2] S. Kitamura, N. Nagaosa and T. Morimoto, Commun. Phys. 3, 63 (2020).

[3] Y. Suzuki, Phys. Rev. B 105, 075201 (2022).