Phonons, electrons and thermal transport in Planckian high T$_c$ materials

TL;DR

This paper investigates the role of phonons and electrons in thermal transport of high T$_c$ superconductors, proposing a Planckian scattering mechanism that explains resistivity features and phonon-electron interactions across doping levels.

Contribution

It introduces the concept of converse Planckian scattering in high T$_c$ materials and links resistivity features to phonon-electron interactions at different doping levels.

Findings

Resistivity kink near 200 K indicates high temperature Planckian electron-phonon scattering.

Thermal diffusivity data shows persistent phonon-electron scattering even at optimal doping.

The absence of a resistivity feature at optimal doping suggests complex scattering dynamics.

Abstract

The room temperature thermal diffusivity of high T$_c$ materials is dominated by phonons. This allows the scattering of phonons by electrons to be discerned. We argue that the measured strength of this scattering suggests a converse Planckian scattering of electrons by phonons across the room temperature phase diagram of these materials. Consistent with this conclusion, the temperature derivative of the resistivity of strongly overdoped cuprates is noted to show a kink at a little below 200 K that we argue should be understood as the onset of a high temperature Planckian $T$-linear scattering of electrons by classical phonons. This kink continuously disappears towards optimal doping, even while strong scattering of phonons by electrons remains visible in the thermal diffusivity, sharpening the long-standing puzzle of the lack of a feature in the $T$-linear resistivity at optimal doping associated to onset of phonon scattering.