Instabilities and Disorder-Driven First-Order Transition of the Vortex Lattice

     Y. Paltiel,1 E. Zeldov,1 Y. Myasoedov,1 M. L. Rappaport,1 G. Jung,1,2 S. Bhattacharya,3,4 M. J. Higgins,3 Z. L. Xiao,5 E. Y.
     Andrei,5 P. L. Gammel,6 and D. J. Bishop6
     1Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel
     2Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
     3NEC Research Institute, 4 Independence Way, Princeton, New Jersey 08540
     4Tata Institute of Fundamental Research, Mumbai-400005, India
     5Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08855
     6Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974

Transport studies in a Corbino disk suggest that the Bragg glass phase undergoes a first-order transition into a disordered solid. This
transition shows sharp reentrant behavior at low fields. In contrast, in the conventional strip configuration, the phase transition is obscured
by the injection of the disordered vortices through the sample edges, which results in the commonly observed vortex instabilities and
smearing of the peak effect in NbSe2 crystals. These features are found to be absent in the Corbino geometry in which the circulating
vortices do not cross the sample edges.