Prediction of anisotropic thermopower of La/sub 2-x/M/sub x/CuO4

The band structure of Pickett et al and the rigid band approximation are used to calculate the thermopower tensors s/sub xx/(T) and S/sub zz/(T)2 for La/sub 2-x/M/sub x/CuO4 where M is Ca, Sr, or Ba. The values of N(epsilon) and v/sub α/(epsilon) come directly from the calculated eigenvalue spectrum, whereas tau(epsilon) requires an additional calculation. If electron-phonon scattering dominates (which provides a reasonable and conservative explanation for the measured rho/sub αα/(T) in samples with linear T-dependence and rrr ≥ 4) then tau(epsilon) is given by 1/tau(epsilon) = 2πλ(epsilon)k/sub B/T/n and λ(epsilon) can be approximated by Σ eta/sub a/(epsilon)/M/sub a/ where eta/sub a/(epsilon) has already been calculated in the rigid muffin tin model. Alternatively, if impurity scattering dominates, one might assume 1/tau(epsilon) α N(epsilon), or possibility 1/tau(epsilon) = const. The results for σ/sub αα/(epsilon) and S/sub αα/(T) for all three models are given. All three models predict moderately large positive (hole-like) behavior of S/sub zz/ and smaller, negative (electron-like) behavior of S/sub xx/