Low energy loop current excitations in a Mott insulator Original Research Article

It has been believed that low energy excitations in a half-filled antiferromagnetic insulator are only spin excitations. In the present work, however, we show that when spin vortices are created, loop currents arise around centers of the spin vortices. This loop current generation is due to an appearance of a fictitious magnetic field; since the presence of spin vortices causes a sign ambiguity of wave functions for electron hoping motion, a phase factor that ensures the single-valuedness of the wave function appears and gives rise to a vector potential for the fictitious magnetic field. A simulation of the ARPES profile for loop current states is performed using a mean field approximation. It exhibits a Fermi arc feature 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.