Shigeji Fujita

FORMATION OF D-WAVE PAIRONS IN CUPRATES VIA LONGITUDINAL-OPTICAL-PHONON EXCHANGE

The d-wave Cooper pairs (pairons) in cuprates with a strong binding along the a- and b-axes are shown to arise from the optical-phonon-exchange attraction.

Quantum Theory of Thermoelectric Power (Seebeck Coefficient)

The conductivity σ is positive, but the Seebeck coefficient S can be positive or negative. We see that in Fig. 1, the measured Seebeck coefficient S in Al at high temperatures (400 – 670 ◦C) is negative, while the S in noble metals (Cu, Ag, Au) are positive (Rossiter & Bass, 1994). Based on the classical statistical idea that different temperatures generate different electron drift velocities, we obtain S = − cV 3ne , (1.4)

ON VAN HOVE SINGULARITIES IN PURE CUBIC CRYSTALS

Sharp peaks (van Hove singularities) occur when the density of states is plotted as a function of the phonon frequency. The singularities, jumps in the derivative of the density of states, occur in three and two dimensions when the constant-frequency plane touches the Brillouin zone boundary and undergoes a curvature inversion. The face-centered cubic lattice is composed of two simple cubic sablattices and one tetragonal sub-lattice. The first (second) major peaks in the observed density of states in aluminum (Al) are shown to arise from the transverse phonons associated with the cubic (tetragonal) sublattices.