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VOLUME 62 (1995) | ISSUE 12 |
PAGE 934
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Thermal conductivity of the superconducting crystals Bi2Sr2CaCu2O8+y in the ab plane
Efimov V. B. , Mezhov-Deglin L. P.
![The results of measurements of the thermal conductivity <i>Ë </i>and the resistivity ρ of three different high<b>-r<sub>c</sub> </b>Bi<sub>2</sub>Sr<sub>2</sub>Cu<sub>2</sub>0<sub>8+)</sub>, crystals in the <i>ab </i>plane in the temperature range 10-140 ë are presented. It was found that 1) the maximum thermal conductivity of the crystals is several times higher than that of previously studied samples; 2) in contrast to the computational results of the theory of electronic heat transport in anisotropic high-T<sub>e</sub> cuprate crystals, the maximum values of the ratio <i>k(T)Ik{T<sub>c</sub>) </i>in Bi<sub>2</sub>Sr<sub>2</sub>CaCu<sub>2</sub>0<sub>8+;y</sub> crystals can reach 2, and just as in the less anisotropic YBa<sub>2</sub>Cu<sub>3</sub>07_<sub>x</sub> crystals, as this ratio increases, the maximum point of the thermal conductivity shifts in the direction of lower temperatures <i>T<sub>m</sub>/T<sub>c</sub>^0A; </i>and 3) the maxima on the curves of <i>k(T) </i>are observed in samples with low resistivity ρ and metallic-type conductivity <i>p(T)~T, </i>in which the electronic component <i>Ë<sub>Å</sub> </i>is comparable in order of magnitude to the total thermal conductivity <i>Ë </i>at temperatures çÜ=ç<sub>Ó</sub>, and in samples whose resistivity increases with decreasing temperature and therefore <i>Ë<sub>Å</sub><Ë. </i>This shows that to explain the appearance of the maxima on the curves <i>Ë(ô) </i>for high<b>-r<sub>c</sub> </b>cuprate crystals in the superconducting state, it is necessary to take into account the increase in not only the electronic component of the thermal conductivity <i>Ë<sub>Å</sub></i>, as is standard in most modern theoretical calculations, but also in the phonon component <i>Ë<sub>Ò</sub> </i>below <i>T<sub>c</sub>. © 1995 American Institute of Physics.</i>](/ps/1223/article_18484_800_head.png)
The results of measurements of the thermal conductivity Ë and the resistivity ρ of three different high-rc Bi2Sr2Cu208+), crystals in the ab plane in the temperature range 10-140 ë are presented. It was found that 1) the maximum thermal conductivity of the crystals is several times higher than that of previously studied samples; 2) in contrast to the computational results of the theory of electronic heat transport in anisotropic high-Te cuprate crystals, the maximum values of the ratio k(T)Ik{Tc) in Bi2Sr2CaCu208+;y crystals can reach 2, and just as in the less anisotropic YBa2Cu307_x crystals, as this ratio increases, the maximum point of the thermal conductivity shifts in the direction of lower temperatures Tm/Tc^0A; and 3) the maxima on the curves of k(T) are observed in samples with low resistivity ρ and metallic-type conductivity p(T)~T, in which the electronic component ËÅ is comparable in order of magnitude to the total thermal conductivity Ë at temperatures çÜ=çÓ, and in samples whose resistivity increases with decreasing temperature and therefore ËÅ<Ë. This shows that to explain the appearance of the maxima on the curves Ë(ô) for high-rc cuprate crystals in the superconducting state, it is necessary to take into account the increase in not only the electronic component of the thermal conductivity ËÅ, as is standard in most modern theoretical calculations, but also in the phonon component ËÒ below Tc. © 1995 American Institute of Physics.
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