Gordeev SN, Zhukov AA, Jansen AG, Gagnon R, Taillefer L
Department of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ, United Kingdom.
Phys Rev Lett. 2000 Nov 20;85(21):4594-7. doi: 10.1103/PhysRevLett.85.4594.
We report on transport measurements of YBa 2Cu 3O (7-delta) single crystals with different oxygen contents in the geometry B, J ||ab (J perpendicularB). Our data show that the vortices become confined between the Cu-O planes below a well-defined temperature at which the effective size 2xi of the vortex core is approximately equal to the period of the Cu-O layers. This confinement strongly increases the vortex liquid freezing temperature. A new melting line is found separating a vortex liquid and a smectic phase, which shows an oscillatory field dependence reflecting differences between commensurate and incommensurate smectic states.
