Expansion of vortex cores by strong electronic correlation in La2-xSrxCuO4 at low magnetic induction

The vortex core radius ρv, defined as the peak position of the supercurrent around the vortex, has been determined by muon spin rotation measurements in the mixed state of La2-xSrxCuO4 for x=0.13, 0.15, and 0.19. At lower doping (x=0.13 and 0.15), ρv(T) increases with decreasing temperature T, which is opposite to the behavior predicted by the conventional theory. Moreover, ρv(T→0) is significantly larger than the Ginzburg-Landau coherence …