YBa2Cu3O7−δ films: Calculation of the thermal conductivity and phonon mean-free path

Abstract

We estimate the phonon mean-free path (mfp) in YBazCu307-6 by performing a theoretical fitting procedure on bulk single-crystal data. This analysis indicates that the mfps of the phonons that are most responsible for the transport of heat are much longer than would be predicted from kinetic theory. These values are incorporated into a recently proposed treatment of the size effect to provide an estimate of the thermal conductivity

Size effect of out-of-plane thermal conductivity of epitaxial YBa2Cu3O7−δ thin films at room temperature measured by photothermal radiometry

“…(13). Richardson et al 15 reached a similar conclusion that the phonon mean free path of YBCO thin film in the ab-plane direction is substantially longer than the kinetic theory predicts. This may be due to the quite broad spectral distribution of phonons responsible for the thermal conductivity of YBCO.…”

“…In a similar manner, the ab-plane phonon mean free path is reported to be smaller than 10 nm. 10,15 As is well known, the reduction of thermal conductivity across or along a thin film occurs by boundary scattering when the mean free path of a phonon is of the order of or larger than the film thickness. However, if we believe the calculated mean free path based on Eq.…”

“…[2][3][4][5][6][7][8][9] Around the same time as the emergence of these fundamental studies in the physical mechanism responsible for high-T c phenomenon, more application oriented researches appeared, which pointed out another fundamental problems in heat transfer arising from the application of high-T c superconductors in the form of thin-films. [10][11][12][13][14] In the absence of thermal conductivity measurement for thin films YBCO at that time (and it is true even today), Richardson et al 15,16 estimated the phonon mean free path in YBCO by performing a theoretical fitting procedure on bulk singlecrystal thermal conductivity data which were already available. Their analysis indicated that the long-wavelength phonons with mean free paths of the order of the crystal thickness contribute significantly to the thermal conductivity up to about 75 K.…”

Thermoelectric Power and Thermal Conductivity of Neutron Irradiated Superconductors YBa2Cu4O8

“…Phonons transporting a prevailing part of heat become more strongly scattered on defects produced by neutron irradiation [31]. It raises the question to what extent a model relating the thermal conductivity reduction with the oxygen removal in the Y123 superconductors [32] may be applied to the more stable Y124 system.…”

Anomalous optical response of Nd1.85Ce0.15CuO4−y superconducting thin films

“…3, the normalized OR remains constant within a factor of 10%-20% over the temperature range of 100-300 K. The small change in the normalized OR of YBCO comes from the fact that the thermal conductivity of the substrate ͑in this case LaAlO 3 ), which affects the measured OR, changes by about 20% in the temperature range of the measurement. 12 In order to investigate about the possibility of current or light induced anomaly in the OR we measure it's dependence on the bias current, optical power, and the chopping frequency. The OR increases linearly with the bias current for all the films, indicating absence of any current induced nonlinear phenomena.…”