Fig. 2: Enhanced valley splitting.

a Valley splitting as function of shear strain and Ge concentration at the optimal WW wavelength λ = 1.68 nm, computed using sp³d⁵s^* tight-binding theory. Here we assume a wide interface, w = 1.9 nm, and electric field, F_z = 2 mV/nm. (Black star refers to Fig. 3). b Line cuts from (a), corresponding to ε_xy = 0 (dashed line) and 0.15% (solid line). c Line cuts from (a), corresponding to \({\bar{n}}_{{{{\rm{Ge}}}}}=0\) (dashed line) and 2.5% (solid line). Only the combination of shear strain and WW is found to significantly enhance the valley splitting.