Effect of an external magnetic field on electron-spin dephasing induced by hyperfine interaction in quantum dots

We investigate the influence of an external magnetic field on spin-phase relaxation of single electrons in semiconductor quantum dots induced by the hyperfine interaction. The basic decay mechanism is attributed to the dispersion of local effective nuclear fields over the ensemble of quantum dots. The characteristics of electron-spin dephasing are analyzed by taking an average over the nuclear-spin distribution. We find that the dephasing rate can be estimated as a spin-precession frequency caused primarily by the mean value of the local nuclear magnetic field. Furthermore, it is shown that the hyperfine interaction does not fully depolarize electron spin. The loss of initial spin polarization during the dephasing process depends strongly on the external magnetic field, leading to the possibility of effective suppression of this mechanism.