INTERNAL FRICTION AND ULTRASONIC ATTENUATION RELATED TO CARRIERS IN HIGH Tc SUPERCONDUCTORS
HUANG YI-NENG (黄以能)a, WANG YE-NING (王业宁)a, CHEN SHA-OU (陈沙鸥)a, ZHOU HAI-LONG (周海龙)a, ZHANG QING-MING (张清明)a, SHEN HUI-MIN (沈惠敏)a, YANG ZHEN (杨震)a, ZHAO ZHONG-XIAN (赵忠贤)b, LIU PENG (刘鹏)b, ZHANG JIN-LONG (张进龙)b, SI WEI-DONG (司卫东)b, CAO GUO-HUI (曹国辉)c
a National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210008, China; b National Laboratory for Superconductivity, Institute of Physics, Academia Sinica, Beijing 100080, China; c Department of Materials Physics, Beijing University of Science and Technology, Beijing 100083, China
Abstract For both BiSrCaCuO and TlBaCaCuO samples, internal frictions (Q-1) in the kHz range reveal a plateau (Q-1p) above Tc and a rapid drop below Tc with the turning points located just at Tc for various samples with different Tc. This anomaly cannot be observed in non-superconducting samples. The ultrasonic attenuation ($\alpha$) in TlBaCaCuO displays similar results to the internal friction. Moreover, it is discovered that the Q-1p is nearly proportional to the carrier density for Y(Pr)BaCuO and Gd(Pr)BaCuO with different Pr contents. These results show that the drop of Q-1 and a below Tc is closely related to superconducting condensation. The Q-1p and $\alpha$p can be explained using coupling-model of carriers with local dynamic distortion because high Tc superconductors are strong-correlation systems. Furthermore, by taking account of the smearing of superconducting gap structure resulting from the recombination of quasi-particles and by modifying the BCS relative jump rate as S(E, E', $\varGamma$) = Re{1-$\Delta$2/[(E-i$\varGamma$)(E'-i$\varGamma$)]}, the calculated results of internal friction and ultrasonic attenuation below Tc are in good agreement with the experimental data. The superconducting gap $\Delta$ and the damping rate $\varGamma$ for both BiSrCaCuO and TlBaCaCuO have also been obtained, they are in accordance with those got by tunneling spectrum and NMR methods, etc.
Received: 15 March 1993
Accepted manuscript online:
PACS:
74.25.Ld
(Mechanical and acoustical properties, elasticity, and ultrasonic Attenuation)
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