Low-field magnetoresistance in GaAs 2D holes

We report low-field magnetotransport data in two-dimensional hole systems in GaAs/AlGaAs heterostructures and quantum wells, in a large density range, $2.5 \times 10^{10} \leq p \leq 4.0 \times 10^{11}$ cm$^{-2}$, with primary focus on samples grown on (311)A GaAs substrates. At high densities, $p \gtrsim 1 \times 10^{11}$ cm$^{-2}$, we observe a remarkably strong positive magnetoresistance. It appears in samples with an anisotropic in-plane mobility and predominantly along the low-mobility direction, and is strongly dependent on the perpendicular electric field and the resulting spin-orbit interaction induced spin-subband population difference. A careful examination of the data reveals that the magnetoresistance must result from a combination of factors including the presence of two spin-subbands, a corrugated quantum well interface which leads to the mobility anisotropy, and possibly weak anti-localization. None of these factors can alone account for the observed positive magnetoresistance. We also present the evolution of the data with density: the magnitude of the positive magnetoresistance decreases with decreasing density until, at the lowest density studied ($p = 2.5 \times 10^{10}$ cm$^{-2}$), it vanishes and is replaced by a weak negative magnetoresistance.Comment: 8 pages, 8 figure

Spin and phase coherence times in Te doped InSb thin films

AbstractWe investigate the low temperature spin and phase coherence times in Te-doped InSb thin films through measurements of antilocalization. It is found that the extracted spin coherence times range from as long as ∼73ps in films with carrier density n≈0.6×1022m3 down to ∼6ps for n≈8.9×1022m3. The dependence on n indicates that the Elliott-Yafet mechanism is responsible for spin decoherence. The measured spin coherence times are in agreement with theoretical predictions when an appropriately weighed momentum scattering time is used. Extracted phase coherence times are inversely proportional to temperature, consistent with phase decoherence via the Nyquist mechanism