Spin splitting of the excited-state subband in GaAs-Al0.3Ga0.7As asymmetric two-layer systems - art. no. 035309

摘要

We track the variation of the Landau-level filling factors for the quantization of the Hall resistance in unbalanced double-quantum-well structures when the electron density is a controlled parameter. We observe that the filling factors associated with adjacent quantum Hall states differ by three for two or more consecutive quantum Hall transitions. The anomalous filling-factor increment results from simultaneous depopulations of a spin-degenerate Landau level of the ground-state subband and a spin-polarized Landau level of the excited-state subband. The locking of the topmost Landau levels to the Fermi level gives rise to the phenomenon in which the Zeeman splitting of the excited-state subband can be mistaken to be enormous enough to match the Landau-level separation of the ground-state subband. The temperature dependence of the quantum Hall states evidences, however, that the exchange enhancement of the g factor for the excited-state subband is rather similar to that for the ground-state subband. [References: 18]