Thermal conductivity of fullerite C60 crystals at low temperatures

Abstract

The thermal conductivity κ of extended crystals of fullerite C60 with transverse dimensions L of the order of a few millimeters is measured at low temperatures (down to 0.6 K). It is found that in the range from 7 to 0.6 K the temperature dependence of the thermal conductivity of the better of the samples is close to cubic, κ(T)∼T3, and the effective phonon mean free path estimated from the measured thermal conductivity and the published value of the specific heat of fullerite [J. R. Olson et al., Science 259, 1145 (1993)] has a value (lp≈0.6 μm) that is practically independent of temperature and much less than L, i.e., the phonon mean free path is limited by strong scattering on defects in the bulk of the sample.