THERMOPOWER OF A ONE-DIMENSIONAL BALLISTIC CONSTRICTION IN THE NONLINEAR REGIME

Measurements of the thermopower of a one-dimensional (1D) ballistic co nstriction are presented and fitted by calculations for a constriction where the local potential at the bottleneck forms a saddle. The calcu lations show that the thermopower can be well approximated by a linear -response formulation far outside its normal range of applicability. p rovided that an appropriate average temperature is assumed. The fits g ive a saddle parameter of omega(y)/omega(x) greater than or equal to 2 , which sets an upper limit of 2.2 meV on the 1D sub-band spacing.