A strong anisotropy of electron spin decoherence is observed in GaAs/(AlGa)As quantum wells grown on a (110) oriented substrate. The spin lifetime of spins perpendicular to the growth direction is about one order of magnitude shorter compared to spins along $[110]$. The spin lifetimes of both spin orientations decrease monotonically above temperatures of 80 and 120 K, respectively. The decrease is very surprising for spins along the $[110]$ direction and cannot be explained by the usual Dyakonov-Perel dephasing mechanism. A novel spin dephasing mechanism is put forward that is based on scattering of electrons between different quantum well subbands.

• Received 29 September 2003

DOI:https://doi.org/10.1103/PhysRevLett.93.147405