A Model with a Singular Electronic Density of States and Some Properties of High-Temperature Superconductors

Abstract

The influence of singularities in the electronic density of states (DOS) on high‐temperature superconductors is studied in the framework of the conventional BCS theory. By using a DOS with singularities at two different points we are able to explain the asymmetry in the isotope exponent α with respect to the point where Tc is maximum. A DOS with a power law singularity reproduces the vanishingly small values of α and large values of R2 = ΔC(Tc)/Cn(Tc), the ratio of the jump in the electronic specific heat to the normal specific heat at T = Tc, observed in certain high‐Tc materials. However, the value of the ratio R1 = 2Δ0/kBTc does not deviate much from its canonical BCS value of 3.53, in agreement with earlier results.

Influence of Molecular Structure on the Optical Property of POSS: a DFT Calculation Based Quantum Chemistry Calculation

“…where E n (k) describes the dispersion of the given band and the integral is determined over the Brillouin zone [17,18]. An alternative representation of the DOS is based on the fact that N n (E) dE is proportional to the number of allowed wave vectors in the n-th band in the energy range from E to E+dE.…”