Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published July 15, 1994 | public
Journal Article Open

Compressibility of the two-dimensional electron gas: Measurements of the zero-field exchange energy and fractional quantum Hall gap


A quantitative study of the compressibility of the two-dimensional electron gas in GaAs heterostrutures is reported. Using a recently developed capacitive technique that avoids the large offset signals characteristic of conventional methods, high-precision compressibility data at both zero and high magnetic field has been obtained. The curious negative sign of the compressibility in certain regimes is shown to be a consequence of electron-electron interactions. Detailed numerical calculations show that the zero-field data are fully consistent with the known exchange energy, provided the finite thickness of the electron gas is properly included. At high magnetic fields, in the extreme quantum limit, the integrated compressibility signal is used to obtain a quantitative measure of the chemical potential discontinuity associated with the nu = 1/3 fractional quantum Hall effect. Comparison with a theoretical model which includes quasiparticle interactions has allowed a determination of the inhomogeneous broadening due to density fluctuations and has provided evidence of a second, apparently distinct, source of disorder. While the origin of this disorder is not fully understood, the data are consistent with simple lifetime broadening of the quasiparticle states.

Additional Information

©1994 The American Physical Society. Received 22 December 1993. It is a pleasure to thank S. Das Sarma, B. I. Halperin, Song He, R. L. Willett, X. Zhu, and especially M. S. Hybertsen, for numerous very useful discussions. We also thank A. L. Efros and F. G. Pikus for their interest in these experiments and for sharing with us the results of their calculations prior to publication. Thanks also to Jun Hu for providing us with initial self-consistent LDA subband calculations; these were very helpful in setting up our own numerical procedures. Finally, we wish to thank A. H. MacDonald for his extensive theoretical help and general interest in this work.


Files (3.9 MB)
Name Size Download all
3.9 MB Preview Download

Additional details

August 22, 2023
August 22, 2023