Quantum wires as Luttinger liquids: experiment

Abstract

The low-temperature ballistic transport properties of quantum wires prepared by the cleaved edge overgrowth method in the GaAs/AlGaAs material system are presented. As the Fermi energy in these one-dimensional (1D) systems is varied by application of a gate voltage a series of quantized conductance plateaus is observed. The plateau values significantly deviate from integer multiples of 2·e 2 /h and show a power law increase with increasing temperature as predicted by Luttinger liquid (LL) theory. The characteristic power law scaling exponent is obtained as a function of the Fermi energy and the number of occupied 1D subbands. From nonlinear current-voltage characteristics across the quantum wires independent LL power law scaling exponents can be deduced. The latter are found to be consistent with those obtained from temperature dependent measurements. In order to rule out contact effects as the only origin of the observed deviations we have investigated a series of quantum wires of different lengths and find quenching of the Luttinger liquid behavior as the wire length is increased. This observation is in agreement with a detailed analysis of reproducable conductance fluctuations which are superimposed on the conductance plateaus.