Electron spin relaxation by nuclei in semiconductor quantum dots

Abstract

We have studied theoretically the electron spin relaxation in semiconductor quantum dots via interaction with nuclear spins. The relaxation is shown to be determined by three processes: (i) -the precession of the electron spin in the hyperfine field of the frozen fluctuation of the nuclear spins; (ii) -the precession of the nuclear spins in the hyperfine field of the electron; and (iii) -the precession of the nuclear spin in the dipole field of its nuclear neighbors. In external magnetic fields the relaxation of electron spins directed along the magnetic field is suppressed. Electron spins directed transverse to the magnetic field relax completely in a time on the order of the precession period of its spin in the field of the frozen fluctuation of the nuclear spins.Comparison with experiment shows that the hyperfine interaction with nuclei may be the dominant mechanism of electron spin relaxation in quantum dots.

Universal quantum control of two-electron spin quantum bits using dynamic nuclear polarization

“…Here we take advantage of the interaction of 1 the electrons with the nuclear magnetic field of the Ga and As sublattices of the host material in order to generate the required magnetic field gradient. While fluctuations of this hyperfine field are known to be a major source of decoherence [8][9][10][11][12] , in this letter we demonstrate the possibility of building up a gradient in the hyperfine field that significantly exceeds the fluctuations and can be sustained for times longer than 30 min. This is done by employing pumping schemes that transfer spin and thus magnetic moment from the electronic system to the nuclei.…”

Decoherence dynamics of a single spin versus spin ensemble

“…The FID line shape is given by the cosine transform of M x ͑t͒. Applying the central limit theorem to this situation, [25][26][27][28] one can find that the FID of a single S spin is approximately Gaussian, with the width given by b = ͱ ͚ k A k 2 -where the coupling parameters A k are determined by the positions of the spins I on a crystal lattice with respect to the given S spin. More generally, the moments of the FID line shape can be calculated directly from Eqs.…”

Electron Spin as a Spectrometer of Nuclear-Spin Noise and Other Fluctuations

“…The study of electron spin evolution subject to the full isotropic hyperfine interaction has attracted a great deal of attention lately [26,27,25,28], particularly because of a series of free induction decay experiments probing electron spin dynamics in quantum dots in the low magnetic field regime [29]. In the author's opinion the most successful theoretical approach so far in the description of these experiments is to treat the collective nuclear spin field classically by taking averages over its direction and magnitude [26]. Here we shall not discuss the interesting effects occurring at low fields.…”