Two-dimensional vortex behavior in highly underdoped YBa_2Cu_3O_{6+x} observed by scanning Hall probe microscopy

摘要

We report scanning Hall probe microscopy of highly underdoped superconductingYBa_2Cu_3O_{6+x} with T_c ranging from 5 to 15 K which showed distinct fluxbundles with less than one superconducting flux quantum (Phi_0) through thesample surface. The sub-Phi_0 features occurred more frequently for lower T_c,were more mobile than conventional vortices, and occurred more readily when thesample was cooled with an in-plane field component. We show that these featuresare consistent with kinked stacks of pancake vortices.