Direction-resolved transport and possible many-body effects in one-dimensional thermopower

A single-particle theory due to Mott predicts a proportionality between the diffusion thermopower and the energy derivative of the logarithm of the co nductance. Measurements of a ballistic ID wire show that the Mott theory re mains valid in the presence of a finite current, and that it leads to a dir ection-sensitive probe of electron transport. We observe an apparent violat ion of the Mott model at low electron densities, when there is a nonquantiz ed plateau in the conductance at 0.7(2e(2)/h). There is as yet no successfu l theoretical explanation of this so called 0.7 structure, but the distinct ive thermopower signature, which deviates from single-particle predictions, may provide the key to a better understanding.