Field-DrivenTopologicalGlass Transition in a Model Flux Line Lattice

We show that the flux line lattice in a model layered high temperature superconductor becomes unstable above a critical magnetic field with respect to a plastic deformation via penetration of pairs of pointlike disclination defects. The instability is characterized by the competition between the elastic and the pinning energies and is essentially assisted by softening of the lattice induced by a dimensional crossover of the fluctuations as field increases. We propose that this mechanism provides a model of the low temperature field-driven disordering transition observed in neutron diffraction experiments on ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_8$ single crystals.