Botzem Tim, McNeil Robert P G, Mol Jan-Michael, Schuh Dieter, Bougeard Dominique, Bluhm Hendrik
JARA-Institute for Quantum Information, RWTH Aachen University, D-52074 Aachen, Germany.
Institut für Experimentelle und Angewandte Physik, Universität Regensburg, D-93040 Regensburg, Germany.
Nat Commun. 2016 Apr 15;7:11170. doi: 10.1038/ncomms11170.
Understanding the decoherence of electron spins in semiconductors due to their interaction with nuclear spins is of fundamental interest as they realize the central spin model and of practical importance for using them as qubits. Interesting effects arise from the quadrupolar interaction of nuclear spins with electric field gradients, which have been shown to suppress diffusive nuclear spin dynamics and might thus enhance electron spin coherence. Here we show experimentally that for gate-defined GaAs quantum dots, quadrupolar broadening of the nuclear Larmor precession reduces electron spin coherence by causing faster decorrelation of transverse nuclear fields. However, this effect disappears for appropriate field directions. Furthermore, we observe an additional modulation of coherence attributed to an anisotropic electronic g-tensor. These results complete our understanding of dephasing in gated quantum dots and point to mitigation strategies. They may also help to unravel unexplained behaviour in self-assembled quantum dots and III-V nanowires.
理解半导体中电子自旋因与核自旋相互作用而产生的退相干，不仅对于实现中心自旋模型具有根本重要性，而且对于将其用作量子比特具有实际意义。核自旋与电场梯度的四极相互作用会产生有趣的效应，已证明这种相互作用会抑制扩散性核自旋动力学，从而可能增强电子自旋相干性。在此，我们通过实验表明，对于栅极定义的砷化镓量子点，核拉莫尔进动的四极展宽会导致横向核场更快去相关，从而降低电子自旋相干性。然而，对于适当的场方向，这种效应会消失。此外，我们观察到归因于各向异性电子g张量的相干性的额外调制。这些结果完善了我们对栅极量子点中退相的理解，并指出了缓解策略。它们还可能有助于揭示自组装量子点和III-V族纳米线中无法解释的行为。
