Some Experimental Prospects involving Parabolic Quantum Wells⁄

We discuss two possible lines of experimental investigation based on parabolic quantum wells. In the flrst proposal, we note that the Generalised Kohn Theorem/Harmonic Potential Theorem forbids electron{electron damping of the Kohn mode in an electron layer gas under strictly parabolic conflnement. This applies even for very strong driving. It is therefore interesting to attempt reduction of other sources of broadening in GaAlAs parabolic wells, so as to achieve a prominent narrow resonance in the far infrared. We concentrate here on phononic bandgap structures, which may be of interest for reduction of phonon efiects in other systems as well. The second class of proposed experiment involves twinned parabolic wells in an attempt to observe van der Waals forces directly in GaAlAs systems. In a flrst approximation, the parabolic or Hooke’s-law nature of the conflnement allows one to use the well as a kind of spring balance to measure the weak van der Waals force. The in°uence of an applied magnetic fleld on these forces appears to be signiflcant, and this system might provide the flrst measurement of such an efiect. 1