Temperature Dependence of Conductance and Thermopower Anomalies of Quantum Point Contacts

It has been shown within the Landauer single-channel approach that the presence of the 0.7 anomaly in the conductance of a ballistic microcontact and the respective plateau in the thermopower implies unusual pinning of the potential barrier height $U$ at a depth of $k_{B}T$ below the Fermi level $E_F$. A simple way of taking into account the effect of electron-electron interaction on the profile and temperature dependence of a smooth one-dimensional potential barrier in the lower spin degeneracy subband of the microcontact has been proposed. The calculated temperature dependences of the conductance and Seebeck coefficient agree with the experimental gate-voltage dependences, including the emergence of anomalous plateaux with an increase in temperature.