Thermal conductivity and electrical resistivity of the high-Tc superconductor YBa2Cu3O9−Δ

Synthesis and characterization of Er-substituted Bi-2223 H-Tc glass–ceramic superconductors

“…Firstly, decrease on the scattering mechanism, because of the superconducting state (T < T c ), and secondly, an increase in the electron mean free path due to decrease in the phonon scattering. In many investigations, the value of the maximum was also found to depend on the preparation method and/or the chemical compositions [42][43][44][45][46][47]. However, it is also important to see the effect of the quasi-particle contribution on the rapid rise of κ(T) below the T c as explained by many groups [35,41].…”

Calculation of the Normal‐State Thermal Conductivity of the Lattice for High‐Tc Superconductors

“…This scattering behaviour due to (6b) has some similarity with the usual phonon-phonon interaction [23]. The dispersion relation E , (12) for the quasilocal excitations behaves like optical phonon modes. The difference between quasilocal excitations and optical phonons consists in the nonperiodicity with respect to reciprocal lattice vectors for (18b).…”

“…also [4]). A similar simplification of (12) has been also performed in [5,6]. In contradiction to the resistivity calculation 141 an explicit function for C(q) is necessary for the calculation of lattice thermal conductivity.…”

“…The difference between quasilocal excitations and optical phonons consists in the nonperiodicity with respect to reciprocal lattice vectors for (18b). The choice of a nonperiodical coupling function C(q) in q-space is the mathematical expression for the quasilocality of the excitations described by (12). In this case the calculation of Aan for the anharmonic model (1 a) is not influenced by umklapp scattering processes between quasilocal excitations.…”

“…Formula (18a) follows from (12) by neglecting the dispersion of the quasilocal excitations (cf. also [4]).…”