Topological defects as relics of emergent continuous symmetry and Higgs condensation of disorder in ferroelectrics

By Shizeng Lin, Xueyun Wang, Y. Kamiya, Gia-Wei Chern, Fei Fan, David Fan, Brian Casas, Yue Liu, V. Kiryukhin, Wojciech H. Zurek and 2 more. Nature Physics, 2014

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Lars Onsager and Richard Feynman envisaged that the three-dimensional (3D) superfluid-to-normal λ transition in 4He occurs through the proliferation of vortices. This process should hold for every phase transition in the same universality class. The role of topological defects in symmetry-breaking phase transitions has become a prime topic in cosmology and high-temperature superconductivity, even though direct imaging of these defects is challenging. Here we show that the U(1) continuous symmetry that emerges at the ferroelectric critical point of multiferroic hexagonal manganites leads to a similar proliferation of vortices. Moreover, the disorder field (vortices) is coupled to an emergent U(1) gauge field, which becomes massive by means of the Higgs mechanism when vortices condense (span the whole system) on heating above the ferroelectric transition temperature. Direct imaging of the vortex network in hexagonal manganites offers unique experimental access to this dual description of the ferroelectric transition, while enabling tests of the Kibble–Zurek mechanism. An imaging study of vortex proliferation near a continuous phase transition in a ferroelectric reveals frozen-in vortices that follow the predictions of the Kibble–Zurek model for cosmological strings formed in the early Universe.

Subfields: Atomic and Molecular Physics, and Optics, Condensed Matter Physics

View Paper: https://www.semanticscholar.org/paper/5126d2de9f43047823957fc5f204e781e49a126f