Effect of frustration on charge dynamics for a doped two-dimensional triangular Hubbard lattice: Comparison with a square lattice

We examine the optical conductivity \sigma(\omega) and the chemical potential \mu, together with the spin correlation, in the strong-coupling limit of a hole-doped two-dimensional triangular Hubbard model near half filling by using an exact diagonalization technique. In contrast to the case of a square lattice without frustration, the doping dependences of \mu and the Drude weight indicate that the charge degree of freedom is weakly coupled to the spin degree of freedom. However, we find that \sigma(\omega) shows strong incoherent excitations extended to a higher energy region. This implies that geometrical frustration in strongly correlated electron systems influences incoherent charge dynamics.