General expressions for the electrical resistivity and thermal conductivity of twinned crystals

TL;DR

This paper derives general expressions for electrical resistivity and thermal conductivity in twinned crystals, applies them to YBa2Cu3O7−δ, and finds twin boundaries have minimal impact on electron scattering but may affect phonons.

Contribution

It introduces new general formulas for transport properties in twinned crystals, considering domain structure and edge effects, and applies them to high-temperature superconductor data.

Findings

Twin boundaries are not a significant source of electron scattering.

Up to 12% suppression of phonon thermal conductivity due to twin boundaries.

Formulas successfully fit experimental data for YBa2Cu3O7−δ.

Abstract

General expressions are derived for the electrical resisitivity and thermal conductivity of a twinned single crystal. Particular attention is paid to the effect of the structure of the twin domains on these transport coefficients. Edge effects are also considered. The expression for the thermal conductivity is used to fit data for a twinned single crystal of 0.8% Zn-doped YBa2Cu3O6.98. The expression for the electrical resistivity is used to fit previously published electrical resistivity data for a twinned single crystal of YBa2Cu3O6.9. It is found that twin boundaries are not a significant source of electron scattering in high-quality single crystals of Y-123. We cannot rule out scattering of phonons by twin boundaries in these crystals, with up to 12% suppression of the phonon component of the thermal conductivity. The related problem of determining the electrical resistivity and thermal conductivity of a crystal with oblique and alternating isotropic regions of different conductivities is also solved.