Giant Spin-Orbit Bowing in GaAs$_{1-x}$Bi$_{x}$

We report a giant bowing of the spin-orbit splitting energy $\Delta _{0}$ in the dilute GaAs$_{1-x}$Bi$_{x}$ alloy for Bi concentrations ranging from 0 to 1.8 {\%}. This is the first observation of a large relativistic correction to the host electronic band structure induced by just a few percent of isoelectronic doping in a semiconductor material. It opens up the possibility of tailoring the spin-orbit splitting in semiconductors for spintronic applications.