MAGNETOCAPACITANCE OSCILLATIONS IN A PERIODICALLY MODULATED 2-DIMENSIONAL ELECTRON-GAS IN THE PRESENCE OF A SMOOTH RANDOM POTENTIAL

We study the density of states (DOS) for a periodically modulated two- dimensional (2D) electronic system in a perpendicular magnetic field i n the presence of a smooth random potential. We find an exact analytic al solution for the DOS which is valid under the conditions that both the period of modulation and the correlation length of random potentia l are larger than the magnetic length. The magnetocapacitance, calcula ted with the use of this DOS, fits nicely the experimental data by Wei ss et al. for the case of one-dimensional periodic potential. The fit of experimental data by Ismail et al. for magnetocapacitance of the sa mples with two-dimensional periodic modulation is also presented.