Abstract
The conductance anomaly is studied in strongly confined, etched GaAs/GaAlAs quantum point contacts, by measuring the differential conductance as a function of source-drain and gate bias as well as a function of temperature. We investigate in detail how, for a given gate voltage, the differential conductance depends on the finite bias voltage and find a so-called self-gating effect, which we correct for. The 0.7 anomaly at zero bias is found to evolve smoothly into a conductance plateau at at finite bias. On varying the gate voltage the transition between the 1.0 and plateaus occurs for definite bias voltages, which define a gate-voltage-dependent energy difference This energy difference is compared with the activation temperature extracted from the experimentally observed activated behavior of the 0.7 anomaly at low bias. We find which lends support to the idea that the conductance anomaly is due to transmission through two conduction channels, of which the one with its subband edge below the chemical potential becomes thermally depopulated as the temperature is increased.
- Received 4 May 2000
DOI:https://doi.org/10.1103/PhysRevB.62.10950
©2000 American Physical Society