Collective flux pinning in hexatic vortex fluid in a-MoGe thin film

Abstract

We investigate the magnetic field variation of the thermally activated flux flow resistivity, ρTAFF and flux flow critical current density, Jc, in a weakly pinned thin film of the amorphous superconductor a-MoGe, where vortices are in a fluid state over a large range of magnetic fields. We show that both quantities can be understood within the framework of collective pinning theory. In particular, our results demonstrate that a ‘peak effect’ can arise at the order–disorder transition of the vortex lattice even when both the ordered and disordered states are vortex fluids, such as the boundary between a hexatic vortex fluid and an isotropic vortex liquid.