Hole-Spin Driving by Strain-Induced Spin-Orbit Interactions

Hole spins in semiconductor quantum dots can be efficiently manipulated with radio-frequency electric fields owing to the strong spin-orbit interactions in the valence bands. Here we show that the motion of the dot in inhomogeneous strain fields gives rise to linear Rashba spin-orbit interactions (with spatially dependent spin-orbit lengths) and $g$-factor modulations that allow for fast Rabi oscillations. Such inhomogeneous strains build up spontaneously in the devices due to process and cool down stress. We discuss spin qubits in $\mathrm{Ge}/\mathrm{GeSi}$ heterostructures as an illustration. We highlight that Rabi frequencies can be enhanced by 1 order of magnitude by shear strain gradients as small as $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}\text{ }\text{ }{\mathrm{nm}}^{\ensuremath{-}1}$ within the dots. This underlines that spins in solids can be very sensitive to strains and opens the way for strain engineering in hole spin devices for quantum information and spintronics.