Hole doping dependence of the coherence length in _x thin films

¹ National Laboratory for Superconductivity, Institute of Physics and Center for Condensed Matter Physics, Chinese Academy of Sciences P.O. Box 603, Beijing 100080, PRC
² Department of Physics, The Pennsylvania State University University Park, PA 16802, USA

Received: 5 August 2003
Accepted: 15 October 2003

Abstract

By measuring the field and temperature dependence of magnetization on systematically doped _x thin films, the critical current density and the collective pinning energy are determined in single-vortex creep regime. Together with the published data of superfluid density, condensation energy and anisotropy, for the first time we derive the doping dependence of the coherence length or vortex core size in wide-doping regime directly from the low-temperature data. It is found that the coherence length drops in the underdoped region and increases in the overdoped side with the increase of hole concentration. The result in the underdoped region clearly prevents from taking the pseudogap energy scale as the upper critical field.