Tuning of the spin-orbit interaction in two-dimensional GaAs holes via strain

We report direct measurements of the spin-orbit interaction-induced spin splitting in a modulation-doped GaAs two-dimensional hole system as a function of anisotropic, in-plane strain. The change in spin-subband densities reveals a remarkably strong dependence of the spin splitting on strain, with up to about 20% enhancement of the splitting upon the application of only about $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ strain. The results are in very good agreement with our numerical calculations of the strain-induced spin splitting.