Ballistic Transport in 1D GaAs/AlGaAs Heterostructures

Abstract

This chapter describes the underlying physics, fabrication, and electrical measurement of ballistic transport in high-mobility, one-dimensional (1D) channels in GaAs heterostructures. After a brief introduction to 2D mesoscopic physics, the chapter introduces important concepts in 1D, including the Landauer formalism, quantum point contacts, saddle point potentials, and the observation of quantized conductance steps in fundamental units of 2 e 2 /h . A historical account of the discovery of conductance quanitsation in n -type GaAs heterostructures will be given, including an overview of different 1D fabrication techniques. We then describe what happens to the quantized conductance plateau as a function of key variables, including magnetic field, temperature, source–drain bias, and carrier density. The 0.7 feature – an anomalous conductance feature at ∼0.7 × 2 e 2 / h is discussed in detail. Finally, we mirror the discussion on electron systems by considering ballistic transport in 1D hole gases. In particular, we highlight the important role that spin–orbit coupling and the large effective mass have on both the single-particle properties and many-body effects in ballistic hole channels.