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Exchange instability of the two-dimensional electron gas in semiconductor quantum wells

A. R. Goñi·U. Haboeck·C. Thomsen·K. Eberl·F. A. Reboredo·C. R. Proetto·F. Guinea
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Abstract

A two-dimensional (2D) electron gas formed in a modulation-doped GaAs/AlGaAs single quantum well undergoes a first-order transition when the first excited subband is occupied with electrons, as the Fermi level is tuned into resonance with the excited subband by applying a dc voltage. Direct evidence for this effect is obtained from low-temperature photoluminescence spectra which display the sudden renormalization of the intersubband energy $E_{01}$ upon the abrupt occupation of the first excited subband. Calculations within density-functional theory, which treat the 2D exchange potential {\it exactly}, show that this thermodynamical instability of the electron system is mainly driven by {\it intersubband} terms of the exchange Coulomb interaction. From temperature-dependent measurements the existence of a critical point at $T_c = 35\pm 5$ K is inferred.

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A. R. Goñi, U. Haboeck, C. Thomsen, K. Eberl, F. A. Reboredo, C. R. Proetto, F. Guinea. 2001-06-22. Exchange instability of the two-dimensional electron gas in semiconductor quantum wells. https://doi.org/10.1103/physrevb.65.121313

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