Phonon-drag thermopower of quantum point contacts

The phonon-drag contribution to the thermopower of a two-dimensional point contact is analyzed. The situation when the contact is wide enough in its narrowest point in the sense that the number of occupied one-dimensional subbands n is much greater than unity, as well as the situation of a quantum point contact (n{~}1) is considered. It is shown that the phonon-drag contribution to the thermopower may appear important and may even prevail over the diffusive contribution, while its quantization picture is shown to differ drastically from that for the diffusive thermopower.