Europhys. Lett.
Volume 47, Number 1, July 1999
Page(s) 104 - 109
Section Condensed matter: electronic structure, electrical, magnetic and optical properties
Published online 01 September 2002
DOI: 10.1209/epl/i1999-00358-9

Europhys. Lett, 47 (1), pp. 104-109 (1999)

Acoustic attenuation study on the normal-state pseudogap in underdoped $\rm YBa_{2}Cu_{3}O_{7-\delta }$

Q. M. Zhang 1, Y. N. Wang 1, A. Li 1, Q. Qiu 1, X. S. Xu 1
Y. Feng 2 and L. Zhou 2

1 National Laboratory of Solid State Microstructures, Institute for Solid State Physics
Center for Advanced Studies in Science and Technology of Microstructures
Nanjing 210093, P. R. China
2 Northwest Institute of Non-ferrous Metal Research - Xi'an 710016, P. R. China

(received 26 January 1999; accepted in final form 29 April 1999)

PACS. 74.25Ld - Mechanical and acoustical properties, elasticity, and ultrasonic attenuation.
PACS. 74.72Bk - Y-based cuprates.


Internal friction (IF) measurement in the kHz frequency region has been performed for underdoped $\rm YBa_{2}Cu_{3}O_{7-\delta }$. A rapid decrease of internal friction with decreasing temperature is observed at a temperature $T_{\rm g}\ ( \gt T_{\rm c} )$, which is considered as the opening of a pseudogap. Based on the feature of pseudogap described by V. J. Emery and BCS theory, a power law decrease of internal friction with temperature at $T_{\rm g}$ is derived and the index is estimated, which is consistent with the experiments. The decrease of the spin-lattice relaxation rate 1/T1 for NMR near 150 K in the underdoped YBCO, similar to that of internal friction, can be explained in the same way. Furthermore, in view of the different phase coherence effect on IF and 1/T1, it can be predicted that another decrease for internal friction will occur near $T_{\rm c}$ but not for 1/T 1. The conclusion is confirmed by the experiments. In addition, the reported anomaly of resistivity near $T^{*}(\sim 160\;{\rm K})$ for the underdoped YBCO is discussed too.


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