Higgs transition from a magnetic Coulomb liquid to a ferromagnet in Yb2Ti2O7
Lieh-Jeng Chang , Shigeki Onoda, Yixi Su, Ying-Jer Kao , Ku-Ding Tsuei , Yukio Yasui, Kazuhisa Kakurai & Martin Richard Lees
Nature Communications, 3, 992 (2012), (DOI: 10.1038/ncomms1989)
Magnetic monopoles can be regarded as the magnetic version of a charged particle like electrons and protons. They carry an isolated magnetic pole, either the North or the South poles. Normally magnets come in the form of dipoles, with both North and South poles appearing in pairs. In a class of magnetic materials called spin ice, four electron spins reside at the four corners of a tetrahedron will be compromised to the spin configuration of 2-in and 2-out toward to the center of the tetrahedron, i.e. obeying the ice rule. When a spin is excited and reverse its direction, there will creat emergent magnetic monopoles, which interact through the magnetic Coulomb law. However, when the spins can rotate away from the “in” and “out” spin configuration because of the quantum-mechanical interactions between the spins, the system is called quantum spin ice. Magnetic monopoles can condense to form a ferromagnet, which can be regarded as the “superconducting” state of monopoles, and is formed through a Higgs mechanism.