2004/10/06 by Yuri Zuev, Yuri L. Zuev, Mun-Seog Kim +2 · 2 citations
Physics and Astronomy · #Magnetic confinement fusion research #Magnetic properties of thin films #Physics of Superconductivity and Magnetism #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevlett.95.137002
4 pages, 2 figures, Submitted to Phys. Rev. Lett
arxiv created 2004/10/06 · openalex publication_date 2005/09/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/04
We report measurements of the ab-plane superfluid density ns (magnetic penetration depth \ensuremathλ) of heavily underdoped films of YBa2Cu3O6+x, with TC's from 6 to 50 K. We find the characteristic length for vortex unbinding transition equal to the film thickness, suggesting strongly coupled CuO2 layers. At the lowest dopings, TC is as much as 5 times larger than the upper limit set by the 2D Kosterlitz-Thouless-Berezinskii transition temperature calculated for individual CuO2 bilayers. Our main finding is that TC is not proportional to ns(0); instead, we find TC\ensuremath∝ns^1/2.3\ifmmode±\else\textpm\fi0.4. This conflicts with a popular point of view that quasi-2D thermal phase fluctuations determine the transition temperature.