Magnetic and charge susceptibilities in the half-filled triangular lattice Hubbard model*

The spin spectra of a triangular system have been studied extensively using the Heisenberg model. But for a correlated metallic triangular system, where the Heisenberg model is not valid, the spin properties are unknown. In this talk, I present momentum-dependent magnetic and charge susceptibilities of the half-filled two-dimensional triangular Hubbard model in the metallic, Mott insulating, and crossover regions of parameter space, using the dual fermion approach. In the insulating state, I find strong spin fluctuations at the K point at low energy corresponding to the 120^o antiferromagnetic order. The spin spectra of the insulating state are consistent with the inelastic neutron spectra of the triangular compound Ba₈CoNb₆O₂₄. I also find that the spin fluctuations at the K point persist into the metallic phase and move to higher energy. These results are in agreement with the studies of spin-lattice relaxation times in k-(ET)₂Cu₂(CN)₃. Finally, I present charge susceptibilities in different areas of parameter space, which should correspond to momentum-resolved electron-loss spectroscopy measurements on triangular compounds.