Pressure dependence of the cyclotron resonance modes in high mobility two-dimensional hole systems in GaAs-(Ga,Al)As heterojunctions

We have performed the first cyclotron resonance studies of high mobility two-dimensional hole systems (2DHS) under pressure. Experiments were carried out using millimetre wave radiation on GaAs-(Ga, Al)As heterojunctions. Pressures were applied using a clamp cell specially designed for millimetre wave measurements. Our data at ambient pressure show collectively coupled resonances arising from interactions between the two hole systems with different effective masses formed by the spin-split halves of the lowest heavy-hole subband. The application of pressure appears to completely suppress the collective effect and only a resonance corresponding to the lighter cyclotron mass from the heavy-hole spin-split subband is observed. (C) 1998 Elsevier Science B.V. All rights reserved.