Magnetothermal conductivity of Ba1-xKxBiO3 crystals

We have investigated the thermal conductivity of single-crystal Ba1-xKxBiO3 (BKBO). The measured temperature and field dependences reveal that both electrons and phonons contribute to the thermal conduction of BKBO in both the normal and the superconducting states, and that the phonon mean free path can be manipulated by potassium doping concentration. The potassium-underdoped samples exhibit a suppression of phonon diffusivity, and consequently a more pronounced electronic contribution, indicating that the statistical fluctuation of potassium concentration may lead to an increase of defect density. The field-dependent thermal conductivity of BKBO in the superconducting state exhibits scaling behavior, which indicates the presence of an unconventional superconducting gap