Loop Current Excitations in Effectively Half-Filled Mott Insulators(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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We show that spin vortex excitations in a two-dimensional half-filled antiferromagnetic insulator are accompanied by loop currents; they are the collective flow of electrons generated by a fictitious magnetic field, where the field arises from a phase factor that ensures the single-valuedness of wave functions for electron hopping motion. We study effectively half-filled states of a U≫t Hubbard model in which all holes added to the exactly half-filled antiferromagnetic insulator become self-trapped polarons. Using the perturbation theory, we demonstrate that loop currents arise when spin vortices are created and partially retrieve the itineracy of electrons in the upper Hubbard band. We also perform mean-field calculations to gain qualitative insights on the loop current state using parameters appropriate for cuprate superconductors. It is shown that a collection of loop currents creates a large current flow region or a "river" of current. A calculated ARPES profile exhibits a Fermi arc feature seen in cuprates when an extended loop current region is present; thus, it is suggested that such a current region may be the origin of the Fermi arc. The elastic neutron scattering cross section profiles are also calculated and a splitting of peaks that resembles experimental results is obtained.
社団法人日本物理学会の論文
2008-03-15