Lifetime broadening of sub-band structure in the thermopower of narrow-channel systems

A Boltzmann equation calculation of the thermopower in narrow-channel systems that exhibit sub-band structure predicts sharp peaks in and changes in sign of this quantity. This is due to large changes in the density of states of the system at energies corresponding to sub-band minima. Structure in the electrical conductivity due to the same property of these systems is found to be significantly smoothed by lifetime-broadening effects such that it could be rendered almost experimentally unobservable. The authors calculate the effects of lifetime broadening on the structure in the thermopower. Since this structure is more marked than in the electrical conductivity the lifetime broadening masks it less easily. Significant structure is predicted to remain for systems that have a k F l value of three in the electric quantum limit.