Bias and temperature dependence of the 0.7 conductance anomaly in Quantum Point Contacts

Abstract

The 0.7 (2e^2/h) 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 0.85 (2e^2/h) at finite bias. Varying the gate voltage the transition between the 1.0 and the 0.85 (2e^2/h) plateaus occurs for definite bias voltages, which defines a gate voltage dependent energy difference $\Delta$. This energy difference is compared with the activation temperature T_a extracted from the experimentally observed activated behavior of the 0.7 anomaly at low bias. We find Δ= k_B T_a 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 Δbelow the chemical potential becomes thermally depopulated as the temperature is increased.

9 pages (RevTex) with 9 figures (some in low resolution)

References in corpus (6)

• Possible Spin Polarization in a One-Dimensional Electron Gas
• Interaction Effects in a One-Dimensional Constriction
• Spin Properties of Low Density One-Dimensional Wires
• Ferromagnetic correlations in quasi-one-dimensional conducting channels
• Temperature dependence of the ``0.7'' 2(e^2)/h quasi plateau in strongly confined quantum point contacts
• Quantum ballistic transport in in-plane-gate transistors showing onset of a novel ferromagnetic phase transition

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