Comparison of 2-D Quantum and Thermal Critical Fluctuations of Underdoped Bi2Sr2CaCu2O8+δ with Ultrathin YBa2Cu3O7−δ
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This paper addresses two issues. Underdoped Bi-2212 has been shown to exhibit two-dimensional quantum fluctuations, with T c vs. N s (0) scaling qualitatively similar to ultrathin YBCO films that are 2-D by construction. The present paper shows that the quantitative difference in scaling is resolved by growing Bi-2212 films that are much smoother than previously used. Also, the absence of 2-D thermal critical behavior from the superfluid density of Bi-2212 films that exhibit 2-D quantum scaling is not likely due to an inhomogeneous T c smearing out the 2-D thermal transition. Finally, we emphasize that there is as yet no consensus on the physics that drives the T-dependence of N s at low to intermediate temperatures.
KeywordsSuperconductivity Quantum critical scaling Pulsed laser deposition Cuprates
This work was supported by Department of Energy-Basic Energy Sciences through Grant No. FG02-08ER46533 and by the Center for Emergent Materials, National Science Foundation MRSEC Grant No. DMR-0820414. We would also like to thank Adam Ahmed for technical assistance.
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