Abstract: Advances
in nanofabrication techniques have given researchers tremendous freedom
to create novel low dimensional devices with unusual quantum transport
behavior. These behaviors are often a result of the reduced
dimensionality, and in particular, may arise from strong electron
correlations. In this talk we present the observation of conductance
anomalies in asymmetric quantum point contacts formed in AlGaAs/GaAs
two dimensional electron gas. The point contacts can be gated and tuned
to a regime with clear e2/h features at zero field, as well as in a regime without any anomalous features below 2e2/h. The e2/h
feature has been thought to be related to possible spontaneous spin
polarization or opening of a spin gap in the quantum point contact
[1-3]. Differential conductance versus source drain bias (dI/dVsd) in the former regime show similar behavior to what was observed previously at 8T [3] with clear bunching at e2/h and 3e2/h, but at zero field. These results point clearly to the role an asymmetric geometry has in enhancing interaction effects.
[1] Thomas et al. PRL 77, 135 (1996)
[2] Reilly et al. PRB 63, 121311 (2001)
[3] Cronenwett et al. PRL 88, 226805 (2002)