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 tw o-dimensional hole systems (2DHS) under pressure. Experiments were carried out using millimetre wave radiation on GaAs-(Ga, Al)As heterojunctions. Pre ssures were applied using a clamp cell specially designed for millimetre wa ve measurements. Our data at ambient pressure show collectively coupled res onances arising from interactions between the two hole systems with differe nt effective masses formed by the spin-split halves of the lowest heavy-hol e subband. The application of pressure appears to completely suppress the c ollective effect and only a resonance corresponding to the lighter cyclotro n mass from the heavy-hole spin-split subband is observed. (C) 1998 Elsevie r Science B.V. All rights reserved.