Vortices in coupled planes with columnar disorder and bosonic ladders

Abstract

We consider two coupled strongly correlated bosonic chains. We derive the phase diagram of the pure system and obtain an antisymmetric charge density wave, a 4k_F charge density wave, a superfluid phase and a second superfluid phase which is a condensate of boson pairs. We consider the effect of a weak disorder on that system and show that the superfluid phase is less localized than in the one chain case. On the other hand, the pinning length of the antisymmetric charge density wave is shorter than in the one chain case. We discuss the consequences of these results for two coupled vortex planes with columnar disorder. We show that in the vortex system there is a conventional pinned solid phase for 0<T<T_m, a pinned solid phase with superkinks for T_m<T<T_L and a vortex liquid for T>T_L. We obtain the critical currents by a modified Larkin-Ovchinnikov argument and prove that there is a strong reduction of critical current for T=T_m.