Spin susceptibility enhancement in a two-dimensional hole gas

The critical spin splitting needed to fully polarize a two-dimensional heavy-hole gas in a (Cd,Mn)Te quantum well thanks to the giant Zeeman effect is measured through photoluminescence and transmission spectroscopy. While the splitting between two circularly polarized peaks in photoluminescence remains equal to the bare spin splitting, the critical spin splitting which governs the polarization is enhanced, in good agreement with the prediction of a model of hole-hole interactions previously applied to conduction electrons. Consequences for carrier-induced ferromagnetism are discussed.