Precise estimation of spin drift velocity and spin mobility in the absence of synthetic Rashba spin-orbit field in a Si metal-oxide-semiconductor

The discovery of built-in and synthetic Rashba fields in Si spin channels [S. Lee et al., Nat. Mater. 20, 1228 (2021)] challenged the conventional understanding of spin transport physics in semiconducting materials and forced researchers to reconsider the procedures used for estimating spin drift velocity and spin mobility. A conventional procedure for the estimation involves the detection of the Hanle-type spin precession under the application of an external magnetic field perpendicular to the plane; however, the in-plane effective magnetic fields due to the built-in Rashba fields hamper precise estimation because of the additional spin precession. In this work, we establish a precise method to estimate spin drift velocity and spin mobility, in addition to the spin lifetime and spin diffusion constant, by appropriately tuning the Rashba fields. Beyond the emblematic case of Si, the established method can be applied to other semiconductors, such as Ge and GaAs.