Faculty Bibliography

We report the experimental observation of the broadening of the frequency spectra of parametrically generated second sound waves by first sound in superfluid He-4. The first experimental evidence of Gaussian statistics of amplitudes of parametrically generated waves is presented. Using the kinetic theory of parametric excitation we suggest that the broadening and exponential tails of spectra result from four-wave resonance interaction in a close analogy with similar-evidence in parametrically generated spin waves. Universality of the exponential tails in the frequency spectra is suggested

The stability of a two-dimensional electron system with negative compressibility is discussed and related to experimental data from magnetocapacitance measurements. A system with a single Landau level as well as one with several Landau levels is investigated

It is shown experimentally that the interactions between electrons strongly influence the chemical potential of the two-dimensional electron gas. At sufficiently low temperatures and in high magnetic fields regions of filling factor appear where (i) the chemical potential diminishes with increasing carrier density, and (ii) the rate of increase of the chemical potential with magnetic field is much higher than the maximum value for a noninteracting gas. Using these results we have estimated the energy of the electron-electron interaction in Si inversion layers which appears to be an order of magnitude less than the classical Coulomb interaction calculated for Si-MOSFET's