Characterization of spin-orbit fields in InGaAs quantum wells

Narrow-gap semiconductors exhibit strong spin-orbit interaction and are therefore of interest for spin-based quantum devices and for Majorana zero modes. We investigate coherent electron-spin dynamics and the size and symmetry of spin-orbit interaction in InGaAs/InAlAs quantum wells from 10 K to room temperature using time-resolved Kerr rotation. The spin lifetime exceeds 1\,ns at 10\,K and decreases with temperature. By imprinting a diffusive velocity on the measured electron spins [1], the spin-orbit energy is measured as a change in spin precession frequency. A Rashba symmetry of the spin-orbit interaction is determined with a Rashba coefficient of 2$\times$10$^{-12}$\,eVm [2]. This technique can be applied to other narrow-gap semiconductors without the need to lithographically process the sample or to apply electrical signals.\newline [1] M.~Kohda {\em et al.}, Appl.~Phys.~Lett.~{\bf 107}, 172402 (2015).\newline [2] T. ~Henn {\em et al.}, Appl.~Phys.~Lett.~{\bf 109}, 152104 (2016).\newline