Transport properties of ballistic One-dimensional electron gases

>Transport in quantum wires has attracted wide interest since the discovery of conductance quantization in 1988. Interest in quantum wires has steadily grown due to theoretical predictions that at low densities electron-electron interactions may give rise to many different effects such as Luttinger liquid phenomenon, Wigner crystallization, spin polarization etc.  While direct observation of Luttinger liquid behavior was found to be elusive in transport experiments, spin-related effects such as the 0.7 structure and zero bias conductance anomaly observed in ballistic quantum wires are believed to be due to interactions. Many theoretical models were proposed to explain the 0.7 structure [1] including spin polarization, Kondo effect, spin-incoherent transport, and Wigner crystallization. One of the important experimental results came after predictions [2] that a tunable confinement potential which competes with the interaction strength may shine light on the origin of the 0.7 structure. Quantum wires were fabricated with an additional top gate to examine the effect of confinement strength and density. We have reported a bifurcation of the 1D electron gas at intermediate strengths of confinement, a possible explanation would be the formation of two spatial rows as interaction strength exceeded the confinement stregth [3,4].  Our recent experiments indicate that a zig-zag configuration could result before such a bifurcation.  In this talk I shall present some of the recent experiments in this regime of transport with emphasis on the implications of lowering confinement strength on the 0.7 structure