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Research
Anti-Ferromagnetism
The high-Tc superconductors evolve from parent, un-doped
compounds that are anti-ferromagnetic insulators. Part of a class
of insulators called “Mott-Hubbard” insulators, these parent
compounds have a half-filled electron band, but do not conduct electricity. Instead,
due to the high on-site coulomb repulsion, a single electron occupies
each copper atom. The electrons interact with the neighboring
electrons only through the anti-ferromagnetic exchange interaction. These
anti-ferromagnetic fluctuations show up as “hot spots” of
depleted intensity along the Fermi-surface of a doped compound. The “hot
spots” are located where the Fermi surface crosses the Brillouin
zone boundary of the anti-ferromagnetic lattice. One of the proposed
mechanisms for “high-Tc” superconductivity is
precisely this anti-ferromagnetic interaction.
