Interband coupling

The dispersion of up in YNi2B2C has been confirmed by de Haas-van Alphen experiments (Goll et al., 1996). The values of Hc2(0) and Tc are reduced by the presence of the fast electrons that have only a moderate el-ph coupling. On the other hand, the positive curvature of H T) is caused by interband coupling between the slow and the fast electrons. In the example of Figure 25 the experimental... 

The non-BCS nature of the interband pairing process is indicated also by the fact that, when it is dominant, the isotope effect vanishes even if the intra-band attractive interaction in each band is due to the electron-phonon coupling. 

Moreover the effective repulsive Coulomb pseudopotential in the Migdal-Eliashberg theory is expected to decrease (so the effective coupling strength increases) where the interband pairing is dominant. 

Also the experimental indications on the essential role of the interband electron-phonon coupling, which follows from the investigation of phonon frequency anomalies at the onset of superconductivity must be mentioned [38]. 

The linearized Hamiltonian describing the pairing via the interband scattering of intraband pairs and the vibronic interband mixing (coupling constant V) is written in the form... 

The enhancement of surface plasmon absorption of metal nanoparticles may be a result of strong near-field coupling in the close-packed copper-silver nanostructure. The effect is more considerable at the spectral range outside of the copper interband absorption that is why it is not evident at the LSPA band of silver nanoparticles. At th e fi equency range near the LSPA band of copper nanoparticles, near-field coupling is not suppressed by die interband absorption so much and the LSPA enhancement is well seen. 

As discussed above, in YBa2Cu307, we have proposed charge transfer excitations of occupied (localized) dpn states, to empty dpa bands as a representation of the interband interactions. In Tl2Ba2CaCu2Dg (and similarly in Bl2Sr2CaCu20g) it becomes clear that the Inturband interactions between the non-bonding 0 p states and the almost empty Tl-0 sp(dpa) bands will lead to virtual excitations which couple to the conduction electrons in the CUO2 planes and may... 

In ordinary optical absorption there are two components associated with intraband transitions (Drude component) and interband transitions, respectively. A similar situation is encountered in magneto-optical spectroscopy. Of special interest is the interband component which is related to the joint density of states. The intensity of the magneto-optical transitions is proportional to the product of spin-orbit coupling strength and net electron-spin polarization of states excited by the incident light (Erskine and Stern, 1973). 

The band structure and the DOS of the orthorhombic 3D Cgo (0-3D) polymer were calculated on the basis of the coordinates obtained by the X-ray refinement and theoretically optimized structures [68, 70, 71]. All of the calculations suggested the metallic conductivity of the 0-3D polymer with a large density of states at the Fermi level. The calculation by Yang et al. [70] suggested that the electronic band structure has steep and flat bands near the Fermi level, and possible occurrence of interband nesting which may enhance electron-phonon coupling for superconductivity. With these features it is possible that the 0-3D Cgo polymer would be a potential superconductor even without doping. The 0-3D polymer is electron... 

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