Tunable Conductance Anomaly in Asymmetrically Gated Quantum Point Contacts

We have observed conductance anomalies in asymmetrically gated quantum point contacts formed in AlGaAs/GaAs two dimensional electron gas. The point contacts can be set in a regime with conductance anomaly that can be tuned continuously from $0.3*2e^2/h$ to $0.7*2e^2/h$, as well as in a regime without any anomalous features below $2e^2/h$. Differential conductance versus source drain bias ($dI/dV_{sd}$) in either regimes show strikingly contrasting behavior.