Dynamic transition from Mott-like to metal-like state of the vortex lattice in a superconducting film with a periodic array of holes

TL;DR

This study demonstrates a transition in vortex lattice behavior in a superconducting film with a periodic hole array, from localized Mott-like to delocalized metal-like states, driven by an AC magnetic field.

Contribution

It reveals a collective, amplitude-dependent transition in vortex states, characterized by sharp response jumps, using magnetic shielding measurements.

Findings

Vortex lattice transitions from localized to delocalized states.

Threshold AC amplitude induces sharp response jumps.

Transition depends on vortex filling fraction.

Abstract

We show that under an a.c. magnetic field excitation the vortex lattice in a superconductor with periodic array of holes can undergo a transition from a Mott-like state where each vortex is localized in a hole, to a metal-like state where the vortices get delocalized. The vortex dynamics is studied through the magnetic shielding response which is measured using a low frequency two-coil mutual inductance technique on a disordered superconducting NbN film having periodic array of holes. We observe that the shielding response of the vortex state is strongly dependent on the amplitude of the a.c. magnetic excitation. At low amplitude the shielding response varies smoothly with excitation amplitude, corresponding to elastic deformation of the vortex lattice. However, above a threshold value of excitation the response shows a series of sharp jumps, signaling the onset of the Mott to metal transition. Quantitative analysis reveals that this is a collective phenomenon which depends on the filling fraction of vortices in the antidot lattice.