The 253rd Special CMSM seminar   

Elucidation of spin dynamics and quantitative estimation of spin-orbit interaction in semiconductors by magneto-optic imaging

Dr. Yoji Kunihashi
NTT Basic Research Laboratories

Date & Time: 13:30 - 15:00, February 1st (Wed), 2023.
Place: 5F conference room (#513-514), Advanced Structural Materials Bldg., Sengen.


  Magneto-optic imaging of electron spins on the basis of Kerr rotation measurement using a pump-probe technique is a powerful tool for investigating spin dynamics in non-magnetic semiconductors. In this seminar, we’ll discuss two topics related to spin dynamics in III–V semiconductor heterostructures observed using time- and spatially resolved Kerr rotation measurement. First, we’ll discuss the spatial mapping of drifting spins in GaAs quantum wells in which two types of spin-orbit interactions (SOIs), i.e., Rashba and Dresselhaus, are balanced, resulting in a persistent spin helix (PSH) state. In the PSH state, effective suppression of spin relaxation results in the maximum spin decay length, which enables observation of the non-linear effect of SOIs. Second, we’ll discuss the quantitative estimation of the SOI parameters using all-optical means for a GaAsBi epitaxial layer. GaAsBi is an attractive material for achieving large SOIs because atoms with a large atomic number significantly enhance intrinsic SOIs. However, the quantitative determination of SOIs in dilute bismide has not been reported. We investigated the strength of the SOIs in GaAsBi thin film using Kerr rotation microscopy. Spatiotemporal mapping of the Kerr rotation in a magnetic field revealed spin precession due to the effective magnetic field induced by SOI. Theoretical calculations revealed that with the GaAsBi heterostructure Rashba SOIs can be 9.1 and 6.7 times larger, respectively, than those with GaAs and InGaAs heterostructures.

Contact: T. Nakatani, email: