Correlated electron phenomena in ultra-low-disorder quantum point contacts and quantum wires

The study of electron interaction effects in one dimensional transport requires heterostructures with ultra-low disorder. We have developed a novel GaAs/AlGaAs structure which avoids the random impurity potential present in conventional surface-gated HEMT devices by using epitaxially grown gates to produce an enhancement mode FET. Our quantum point contacts (QPCs) exhibit almost ideal conductance quantisation, however, below 2e/sup 2//h additional structure is observed. Such structure has also been seen in QPCs fabricated from ultra-high-mobility surface gated HEMTs and has been interpreted as evidence for a spin-correlated state. In our quantum wire devices this additional structure is further enhanced, indicating that the effective length of the 1D region may be a significant factor in determining the strength of correlation.