Europhys. Lett, 47 (1), pp. 104-109 (1999)
Acoustic attenuation study on the normal-state pseudogap in underdoped
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
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
PACS. 74.72Bk - Y-based cuprates.
Internal friction (IF) measurement in the kHz frequency region has been performed for underdoped . A rapid decrease of internal friction with decreasing temperature is observed at a temperature , 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 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 but not for 1/T 1. The conclusion is confirmed by the experiments. In addition, the reported anomaly of resistivity near for the underdoped YBCO is discussed too.
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