Negative and Positive Magnetoresistance in Variable-Range Hopping Regime of Undoped AlxIn1−xSb/InSb Quantum Wells
Low-temperature magnetoresistance (MR) in the variable-range hopping (VRH) regime of undoped AlxIn1−xSb/InSb quantum wells was studied. The low-T resistance shows that the two dimensional (2D) Mott VRH crossovers to Efros-Shklovskii (ES) VRH due to the Coulomb interaction with lowering T. The anisotropic negative MR in weak magnetic fields was explained by the quantum interference in the VRH. The in-plane positive MR in higher fields found in ES VRH regime was attributed to the spin-Zeeman effect that suppresses the hops between singly occupied states in the presence of intra-state correlation. As for the orbital MR subtracted from perpendicular MR, in deeply insulating regime the negative MR saturates above a characteristic field followed by an exponential increase of the positive MR in agreement with the quantum interference and the subsequent shrinkage of wave functions with increasing field, while in barely insulating regime of the 2D metal-insulator (MI) transition a large negative MR inexplicable survives even in the extremely high magnetic-fields.
KeywordsAnisotropy Shrinkage Coherence GaAs
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- 6.Nguyen V. L., Spivak B. Z. and Shklovskii B. I.: Sov. Phys.-JETP 62, 1021–1029, 1985Google Scholar