Berlin 2005 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 6: Optische Eigenschaften
HL 6.1: Vortrag
Freitag, 4. März 2005, 10:45–11:00, TU P-N229
Dependence on Well Width of the Exchange Instability in Dilute 2D Electron Gases — •Paula Giudici1, Alejandro R. Goñi1,2, Christian Thomsen1, Maik Hauser3, and Karl Eberl3 — 1Institut für Festkörperphysik, PN5-4, Hardenbergstr. 36, 10623 Berlin — 2Institut de Ciència de Materials de Barcelona, Campus de la UAB, 08193 Bellaterra, Spain — 3MPI für Festkörperfoschung, Heisenbergstr. 1, 70569 Stuttgart
High-mobility two-dimensional electron gases (2DEG) realized in modulation-doped GaAs single quantum well (SQW) structures are particularly suitable for studies of the many-body behavior of dilute electron systems. Recently, we have shown that a 2DEG undergoes a first-order phase transition when the first-excited subband becomes populated. Furthermore, the occurrence of a spontaneous breakdown of the spin symmetry was predicted, leading to the formation of a ferromagnetic phase. The existence of the spin instability was confirmed by PL and inelastic light scattering experiments at low effective temperatures of the electron gas. In this work we investigate the dependence of the phenomenology of the exchange instability on the SQW-width. For this purpose we studied the emission spectra of three SQW samples which differ only in the well width (20, 25 and 30 nm). The renormalization energy of the spin-polarized phase presents a clear trend for the studied QW widths. This dependence on well thickness indicates that the strength of the exchange interactions is a function of the confinement of the electron wave functions.