Dimensional reduction and odd-frequency pairing

of the checkerboard lattice Hubbard model

Kazuo Ueda

Institute for Solid State Physics, University of Tokyo, Japan


    The ferromagnetism of the checkerboard lattice Hubbard model at quarter filling found by Mielke is one of the few exact ferromagnetic ground states known in the family of Hubbard models. When the nearest neighbor hopping, t1, is small compared with the second neighbor one, t2, the system reduces to a collection of Hubbard chains. We find that the 1D character is surprisingly robust as long as t1 < t2.  This phenomenon of dimensional reduction is a consequence of the effects of geometrical frustration on itinerant electrons, which leads to peculiar magnetic orders with 1D character for intermediate U.  It is found that odd-frequency superconducting states are stable in a wide parameter range close to the magnetic instability line.

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