Abstract
We performed NMR studies on two overdoped high-quality ( and 1.0) single crystals. In the normal states, we found a dramatic increase in the spin-lattice relaxation from the to the samples. In , the ratio of , where is the Knight shift, increases as temperature drops. These results indicate the existence of another type of spin fluctuations in which is accustomed to being treated as a simple Fermi liquid. In the superconducting state, the temperature scalings of below in the overdoped samples are significantly different from those in the under or optimally doped ones. A power-law scaling behavior is observed, which indicates universal strong low-energy excitations in the overdoped hole-type superconductors.
- Received 1 September 2009
DOI:https://doi.org/10.1103/PhysRevB.81.012503
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