PROXIMITY EFFECT IN THE COLLECTIVE EXCITATIONS OF THE FRACTIONAL QUANTUM HALL STATE

We present calculations of the collective excitation spectrum of the fractional quantum Hall state in the presence of the proximity effect (i.e., the effect of a metallic layer close to the two-dimensional electron gas). The gap in the spectrum becomes smaller due to this effect and decreases as the metallic layer gets closer to the electron gas. Increasing the thickness of the electron gas has the same effect as changing the distance to the metallic layer. The proximity effect can be helpful in investigating the role of the electron-electron interactions in the excitations of the fractional quantum Hall state. © 1990 The American Physical Society.