Quantum interference effects and spin-orbit interaction in quasi-one-dimensional wires and rings

We study two kinds of quantum interference effects in transport–the Aharonov-Bohm effect and the weak-localization effect–in quasi-one-dimensional wires and rings to address issues concerning the phase-coherence length, spin-orbit scattering, and the flux cancellation mechanism which is predicted to be present when the elastic mean free path exceeds the sample width. Our devices are fabricated on GaAs/Al_xGa_1-xAs and pseudomorphic Ga_xIn_1-xAs/Al_xIn_1-xAs heterostructure materials and the experiments carried out at 0.4–20 K temperatures. In the GaAs/Al_xGa_1-xAs devices which exhibit no significant spin-orbit scattering, we were able to extract a phase-coherence length l_φ from the amplitude of the Aharonov-Bohm magnetoresistance oscillations in different sized rings. We find it to be in agreement with l_φ deduced from the weak-localization data in parallel wires when the one-dimensional weak-localization theory including the flux cancellation mechanism is used to fit the data. We therefore unambiguously establish that the same l_φ governs the behavior of the two quantum interference phenomena of Aharonov-Bohm oscillations and weak localization, and that the flux cancellation is in force. In the pseudomorphic Ga_xIn_1-xAs/Al_xIn_1-xAs heterostructure devices which exhibit strong spin-orbit interaction effects, l_φ exceeds the spin-orbit-scattering length at low temperatures. The amplitude of Aharonov-Bohm oscillations can only be explained by introducing reduction factors due to spin-orbit scattering.