Charge Order on Triangular Lattice: Atomic Limit, Mean Field and Dynamical Mean Field
Aleksey Alekseev, ISQI, Faculty of Physics and Astronomy, Adam Mickiewicz University Poznań

Triangular-lattice models can describe a number of strongly correlated materials that exhibit superconductivity, various magnetic and charge orders, including exotic and frustration-induced ones, topological states, and more. Here, we focus on charge-ordering phenomena utilizing the extended Hubbard model with repulsive onsite and intersite interactions and on the grand-canonical ensemble with all-encompassing range of chemical potentials. We have identified a large number of various phases, phase transitions, and features of the phase diagram of the triangular lattice, such as the strong particle-hole asymmetry, phase separation states, exotic pinball-liquid phase, or changeable nature of the symmetry breaking. We provided their detailed analysis and received a lot of insight from the evolution of the phase-diagram features within the series of methods: atomic limit solution, mean-field approximation, and dynamical mean-field theory. The resulting phase diagram from the dynamical mean-field theory is unexpectedly complex and can be used to interpret the charge order in many real materials that have triangular-lattice structure.