Spin echo decay at low magnetic fields in a nuclear spin bath

Łukasz Cywiński, V. V. Dobrovitski, and S. Das Sarma
Phys. Rev. B 82, 035315 – Published 23 July 2010

Abstract

We investigate theoretically the spin echo signal of an electron localized in a quantum dot and interacting with a bath of nuclear spins. We consider the regime of very low magnetic fields (corresponding to fields as low as a militesla in realistic GaAs and InGaAs dots). We use both the exact numerical simulations and the analytical theory employing the effective pure dephasing Hamiltonian. The comparison shows that the latter approach describes very well the spin echo decay at magnetic fields larger than the typical Overhauser field, and that the time scale at which this theory works is larger than previously expected. The numerical simulations are also done for very low values of electron spin splitting at which the effective Hamiltonian based theory fails quantitatively. Interestingly, the qualitative difference in the spin echo decay between the cases of a homonuclear and a heteronuclear bath (i.e., bath containing nuclear isotopes having different Zeeman energies), predicted previously using the effective Hamiltonian approach, is still visible at very low fields outside the regime of applicability of the analytical theory. We have found that the spin echo signal for a homonuclear bath oscillates with a frequency corresponding to the Zeeman splitting of the single nuclear isotope present in the bath. The physics behind this feature is similar to that of the electron spin echo envelope modulation. While purely isotropic hyperfine interactions are present in our system, the tilting of the electron precession axis at low fields may explain this result.

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  • Received 2 April 2010

DOI:https://doi.org/10.1103/PhysRevB.82.035315

©2010 American Physical Society

Authors & Affiliations

Łukasz Cywiński1,2,*, V. V. Dobrovitski3, and S. Das Sarma2

  • 1Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, PL 02-668 Warszawa, Poland
  • 2Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
  • 3Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA

  • *Electronic address: lcyw@ifpan.edu.pl

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Vol. 82, Iss. 3 — 15 July 2010

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