Quantum Thermal Conductance of Electrons in a One-Dimensional Wire

An electron thermometer was used to measure the temperature rise of approximately 2 × 10⁵ electrons in a two-dimensional box, due to heat flow into the box through a ballistic one-dimensional (1D) constriction. Using a simple model we deduce the thermal conductance κ(Vg) of the 1D constriction and compare it to the electrical conductance characteristics. For the first four 1D subbands the heat carried by the electrons passing through the wire is proportional to its electrical conductance G(V_g). In the vicinity of the 0.7 structure this proportionality breaks down, and a plateau at the thermal-conductance quantum, π2k2_B T/3h, is observed. [Phys. Rev. Lett. 97, 056601 (2006)]