Persistence of Metastable Vortex Lattice Domains in MgB2 in the Presence of Vortex Motion

TL;DR

This study investigates the persistence of metastable vortex lattice domains in MgB2, revealing that their stability is due to domain jamming rather than vortex pinning, even during vortex motion.

Contribution

It provides new insight into vortex lattice metastability by demonstrating that domain jamming, not pinning, maintains metastable states in MgB2.

Findings

Metastable vortex domains persist despite vortex motion.

Metastability is not caused by vortex pinning.

Jamming of domains prevents transition to ground state.

Abstract

Recently, extensive vortex lattice metastability was reported in MgB2 in connection with a second-order rotational phase transition. However, the mechanism responsible for these well-ordered metastable vortex lattice phases is not well understood. Using small-angle neutron scattering, we studied the vortex lattice in MgB2 as it was driven from a metastable to the ground state through a series of small changes in the applied magnetic field. Our results show that metastable vortex lattice domains persist in the presence of substantial vortex motion and directly demonstrate that the metastability is not due to vortex pinning. Instead, we propose that it is due to the jamming of counterrotated vortex lattice domains which prevents a rotation to the ground state orientation.