Giant anisotropy of spin relaxation and spin-valley mixing in a silicon quantum dot

Xin Zhang, Rui-Zi Hu, Hai-Ou Li, Fang-Ming Jing, Yuan Zhou, Rong-Long Ma, Ming Ni, Gang Luo, Gang Cao, Gui-Lei Wang, Xuedong Hu, Hong-Wen Jiang, Guang-Can Guo, Guo-Ping Guo

Published 2019-12-18Version 1

It is well known that for Si quantum dots (QDs), at a certain magnetic field that is commonly referred to as the "hot spot", the electron spin relaxation rate (T_1^(-1)) can be drastically enhanced due to strong spin-valley mixing. Here, we experimentally find that with a valley splitting of ~78 {\mu}eV, this "hot spot" spin relaxation can be suppressed by more than 2 orders of magnitude when the in-plane magnetic field is oriented at an optimal angle, about 9{\deg} from the [100] sample plane. This directional anisotropy exhibits a sinusoidal modulation with a 180{\deg} periodicity. We explain the magnitude and phase of this modulation using a model that accounts for both spin-valley mixing and intravalley spin-orbit mixing. The generality of this phenomenon is also confirmed by tuning the electric field and the valley splitting up to ~268 {\mu}eV.