Spin hot spots in single‐electron GaAs‐based quantum dots

Abstract

Spin relaxation of a single electron in a weakly coupled double quantum dot is calculated numerically. The phonon‐assisted spin flip is allowed by the presence of the linear and cubic spin–orbit couplings and nuclear spins. The rate is calculated as a function of the interdot coupling, the magnetic field strength and orientation, and the dot bias. In an in‐plane magnetic field, the rate is strongly anisotropic with respect to the magnetic field orientation, due to the anisotropy of the spin–orbit interactions. The nuclear spin influence is negligible. In an out‐of‐plane field, the nuclear spins play a more important role due selection rules imposed on the spin–orbit couplings. Our theory shows a very good agreement with data measured by Srinivasa et al. [Phys. Rev. Lett. 110, 196803 (2013)], allowing us to extract information on the linear spin–orbit interactions strengths in that experiment. We estimate that they correspond to spin–orbit lengths of about 5–15 μm.

Optimal geometry of lateral GaAs and Si/SiGe quantum dots for electrical control of spin qubits

“…Since it is usually difficult to extract the values of spin-orbit lengths precisely in a quantum dot [7,55], we now consider three limiting cases of, respectively, dominant Rashba, dominant Dresselhaus, and equal spin-orbit strengths. The optimal parameters for these cases, are given in Table I and can be used as general guidelines for maximizing the figure of merit when only a rough estimate of the spin-orbit strengths is available.…”

“…This is due to the rotational (quasirotational) symmetry of the Rashba (Dresselhaus) spin-orbit interaction. Finally, if the relative sign of the spin-orbit interactions is known, which seems easier to extract experimentally than the strengths themselves [7,55], we show that a dot with the main axis along, depending on the sign, [110] or [110], is a robust optimal design for experiments where a vector magnet is available.…”

Control of a spin qubit in a lateral GaAs quantum dot based on symmetry of gating potential

“…Since we assume no doping of the GaAs material [32], l so can be considered constant. Moreover, the relation l so ≫ l [29,33] is satisfied in GaAs QDs, meaning that SOI can be treated as a perturbation. Without SOI, qubit states can be defined as |Ψ 0 ± = |Ψ 0 ⊗ |± , where |Ψ 0 corresponds to the ground state of the spin-independent Hamiltonian H 0 .…”

“…where K TA = |g|µ B B/ c TA . We assume a typical confinement length l = 10nm [29,33] of the GaAs QD in an experimental setup and magnetic field up to a few T…”