Effect of frustration on optical conductivity in a two-dimensional triangular Hubbard model near half filling

We examine the regular part of optical conductivity in the strong-coupling limit of a hole-doped two-dimensional triangular Hubbard model near half filling. A numerically exact diagonalization method based on the Lanczos technique is employed for a 21-site triangular lattice. The regular part is calculated by averaging over various twisted boundary conditions to reduce finite-size effects. We find that the spectra show strong incoherent excitations extended to a higher energy region irrespective of the sign of the hopping amplitude. This is in contrast to the case of a square lattice without frustration. The results imply that geometrical frustration in strongly correlated electron systems influences incoherent charge dynamics.

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