Zero-field spin-splitting in InAs/AlSb quantum wells

Zero magnetic field spin-splitting of two-dimensional conduction band electrons in InAs/AlSb multi-quantum wells is observed in intersub-band absorption experiments. An in-plane magnetic field induces combined spin-flip intersub-band transitions. which for magnetic fields B>0 T are separated in energy by as much as Delta E=17 meV. With increasing magnetic field this separation diminishes and a crossover between both resonances occurs at similar to B similar to 12 T. The excitation of spin-flip resonances, as well as the zero-field spin-splitting, are direct consequences of the bulk inversion asymmetry of InAs, providing two independent methods of determining the relevant band-structure parameter.