Search for Cooper-pair fluctuations in severely underdoped Y1−δCaδBa2Cu3O6+x films (δ=0 and 0.2)

Department of Physics, The Ohio State University, Columbus, Ohio, United States
Physical Review B (Impact Factor: 3.74). 07/2006; 74(1). DOI: 10.1103/PhysRevB.74.012502
Source: arXiv


The preformed-pairs theory of pseudogap physics in high- TC superconductors predicts a nonanalytic T dependence for the ab -plane superfluid fraction, rhoS , at low temperatures in underdoped cuprates. We report high-precision measurements of rhoS(T) on severely underdoped YBa2Cu3O6+x and Y0.8Ca0.2Ba2Cu3O6+x films. At low T , rhoS looks more like 1-T2 than 1-T3/2 , in disagreement with theory.