Thermal measurements of a one-dimensional wire in the quantum limit

Abstract

The single-particle properties of a ballistic one-dimensional (1D) conductorare reviewed; the breakdown in these properties is used to characterize the0.7 structure, an anomalous but reproducible feature in the conductanceG that ismeasured at G = 0.7 × 2e2/h.We show how alternating current heating creates a temperature differenceΔT across a 1D wire, allowing thermopower measurements. The thermopower characteristicsS(Vg) show deviations from Cutler–Mott predictions (a single-particle theory) close tothe 0.7 structure. The magnitude of a thermovoltage peak is used to measurethe electron temperature, and we have incorporated a mesoscopic thermometerinto a simple thermal circuit that allows us to measure the thermal conductanceof a 1D wire. For the first four 1D subbands the heat carried by electronspassing through the 1D constriction is proportional to the electrical conductanceG(Vg); this is the first demonstration that the thermal conductance due to electronsis quantized. In the vicinity of the 0.7 structure the Wiedemann–Franzratio breaks down, and a plateau at the quantum of thermal conductanceπ2kB2T/3h is observed.