Nonequilibrium structural phase transitions of the vortex lattice in MgB2

E. R. Louden, C. Rastovski, L. Debeer-Schmitt, C. D. Dewhurst, N. D. Zhigadlo, M. R. Eskildsen

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7 Scopus citations

Abstract

We have studied nonequilibrium phase transitions in the vortex lattice in superconducting MgB2, where metastable states are observed in connection with an intrinsically continuous rotation transition. Using small-angle neutron scattering and a stop-motion technique, we investigated the manner in which the metastable vortex lattice returns to the equilibrium state under the influence of an ac magnetic field. This shows a qualitative difference between the supercooled case which undergoes a discontinuous transition and the superheated case where the transition to the equilibrium state is continuous. In both cases, the transition may be described by an activated process, with an activation barrier that increases as the metastable state is suppressed, as previously reported for the supercooled vortex lattice [Louden, Phys. Rev. B 99, 060502(R) (2019).2469-995010.1103/PhysRevB.99.060502] Separate preparations of superheated metastable vortex lattices with different domain populations showed an identical transition toward the equilibrium state. This provides further evidence that the vortex lattice metastability, and the kinetics associated with the transition to the equilibrium state, is governed by nucleation and growth of domains and the associated domain boundaries.

Original languageEnglish
Article number144515
JournalPhysical Review B
Volume99
Issue number14
DOIs
StatePublished - Apr 17 2019

Funding

We are grateful to J. Karpinski for providing the MgB 2 single crystal used for this work. We acknowledge useful discussions with E. M. Forgan, B. Janko, K. Newman, M. Pleimlimg, and U. C. Täuber, and assistance with the SANS experiments and data analysis from J. Archer, S. J. Kuhn, and A. Leishman. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Award No. DE-SC0005051. A portion of this research used resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.

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