Thermopower of Single-Channel Disordered and Chaotic Conductors

Abstract

We show (analytically and by numerical simulation) that the zero-temperature limit of the distribution of the thermopower S of a one-dimensional disordered wire in the localized regime is a Lorentzian, with a disorder-independent width of 4 pi^3 k_B^2 T/3eΔ(where T is the temperature and Δthe mean level spacing). Upon raising the temperature the distribution crosses over to an exponential form exp(-2|S|eT/Δ). We also consider the case of a chaotic quantum dot with two single-channel ballistic point contacts. The distribution of S then has a cusp at S=0 and a tail |S|^{-1-β} log|S| for large S (with β=1,2 depending on the presence or absence of time-reversal symmetry).