Abstract
The ab-plane thermal conductivity κ(T) of insulating and superconducting is measured from T=10 to 300 K on single-crystal samples. Metallic has a significantly higher κ than ; the difference Δκ agrees well in magnitude with a Wiedemann-Franz estimate of the electronic contribution to κ in . The shape of κ(T) in insulating differs from normal insulators described by the Peierls-Boltzmann theory. Assuming that atomic vibrations are the main heat carrier, and noting that κ is more similar to that of silica glass than to a normal insulating crystal like CuO, we suggest that the ‘‘phonon’’ mean free path is sufficiently short that the Peierls-Boltzmann theory is not applicable. This is consistent with evidence from neutron scattering that phonons are poorly defined. Our data support the idea that the peak in κ(T) observed below in superconducting samples originates from electronic rather than vibrational heat currents.
- Received 28 October 1993
DOI:https://doi.org/10.1103/PhysRevB.49.9073
©1994 American Physical Society