Hole spin dephasing induced by the lattice
nuclei in semiconductor quantum dots
B. Eble1, P. Desfonds1, F. Fras1, F. Bernardot1, X. Marie2, A. Balocchi2, T. Amand2, A.
Lemaître3, A. Miard3, C. Testelin1 and M. Chamarro1
1
Institut des Nanosciences de Paris, Université P. et M. Curie, CNRS-UMR 7588, 140 rue de
Lourmel, F-75015 Paris, France
2
Université de Toulouse; INSA, UPS, CNRS ; LPCNO, 135 avenue de Rangueil, F-31077
Toulouse, France
(3)
Laboratoire de Photonique et Nanostructures, CNRS, Route de Nozay, F-91460
Marcoussis, France
The electron and the hole, a vacancy of electron in the valence band, are particles with
opposite charges governing semiconductor properties. Both of them carry a magnetic
moment, due to their non-zero spins. Recently, the spin of a single electron localized on
nanometer scale has been proposed as a promising candidate for the realization of solid-statebased quantum bits. The hyperfine interaction of the electron spin with the bath of nuclear
spins in the host material is the main source of the decoherence of spin qubits at low
temperature, when relaxation effects due to phonons can be neglected. Up to now several
experiments have been centered on the hyperfine coupling of conduction electrons [1,2]. For a
hole, this coupling is expected to be much weaker than for an electron because of the psymmetry of the valence band [3].
Here, by confining a hole in an InAs quantum dot, we measure, for the first time, the
coupling between holes and nuclear spins [4]. Indeed, we studied the carrier spin dynamics in
p-doped InAs/GaAs quantum dots by pump-probe photo-induced circular dichroism and timeresolved photoluminescence experiments. We show that the hole spin dephasing is controlled
by the hyperfine interaction between hole and nuclear spins. In the absence of external
magnetic field, we find a characteristic hole spin dephasing time of 15 ns, in close agreement
with our calculations based on dipole-dipole coupling between the hole and the quantum dot
nuclei. We also compare this interaction with the interaction of nuclear spins with the spin of
the photo-created electron and we demonstrate that even if the hole-nuclear spins coupling is
about one order of magnitude weaker than the electron nuclear spin coupling it cannot be
neglected. These results are of primary importance for spin cooling and initialization
techniques required for future spin based information processing.
[1]P.-F. Braun et al. Direct Observation of the Electron Spin Relaxation Induced by Nuclei in
Quantum Dots Phys. Rev. Lett. 94, 116601 (2005)
[2]Johnson, A.C., Petta, J.R. , Taylor J.M., Yacoby A. Lukin M.D. Marcus, M.P. and Gossard
A.C. Nature 435, 925, (2005).
[3]Gryncharova E.I. and Perel V.I., Relaxation of nuclear spins interacting with holes in
semiconductors, Sov. Phys. Semicond. 11, 997 (1977).
[4] B. Eble et al. "Hole-nuclear spin interaction in quantum dots" Phys. Rev. Lett. (in press).
B. Eble et al. arXiv:0807.0968