Spin-Orbit Echo

Preserving and controlling the quantum information content of spins is a central challenge of spintronics. In solids, the relativistic spin-orbit interaction (SOI) leads to a finite spin lifetime. Here, we show that spin information is preserved by the hidden conserved twisted spin and survives elastic disorder scatterings. This twisted spin is an adiabatic invariant with respect to a slow change in the SOI. We predict an echo phenomenon, spin-orbit echo, which indicates the recovery of the spin moment when the SOI is tuned off adiabatically, even after spin relaxation has occurred; this is confirmed by numerical simulations. A concrete experiment in two-dimensional semiconductor quantum wells with Rashba-Dresselhaus SOI is proposed to verify our prediction.