Spontaneously broken time-reversal symmetry in high-temperature superconductors

Mikael Håkansson; Tomas Löfwander; Mikael Fogelström

doi:10.1038/nphys3383

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arXiv · 1411.0886

Spontaneously broken time-reversal symmetry in high-temperature superconductors

Mikael Håkansson·Tomas Löfwander·Mikael Fogelström

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Abstract

Conventional superconductors are strong diamagnets that through the Meissner effect expel magnetic fields. It would therefore be surprising if a superconducting ground state would support spontaneous magnetics fields. Such time-reversal symmetry broken states have been proposed for the high-temperature superconductors, but their identification remains experimentally controversial. Here we show a route to a low-temperature superconducting state with broken time-reversal symmetry that may accommodate currently conflicting experiments. This state is characterised by an unusual vortex pattern in the form of a necklace of fractional vortices around the perimeter of the material, where neighbouring vortices have opposite current circulation. This vortex pattern is a result of a spectral rearrangement of current carrying states near the surfaces.

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Mikael Håkansson, Tomas Löfwander, Mikael Fogelström. 2014-11-04. Spontaneously broken time-reversal symmetry in high-temperature superconductors. https://doi.org/10.1038/nphys3383

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