Phase diagram of the Hubbard model: A cluster slave-spin study
Abstract
We review the study of a cluster spin method in the Hubbard model. Based on the spin chargeseparation theory, the electron operator is decomposed into the product of a fermionic spinon and aslave spin $(S=1/2)$, which represents the physical charge and spin degrees of freedom, respectively.Zeng et al. confirmed the first-order metal-insulator Mott transition in the paramagnetic statein a square lattice based on the saddle point approximation. Moreover, the relationship betweenthe staggered magnetization and the antiferromagnetic gap is established through asymptoticexpansion. They systematically investigated the staggered magnetization with doping and couplingstrength as parameters. Zeng et al. confirmed the absence of the intermediate spin liquid statein the honeycomb lattice and the first-order metal-insulator Mott transition in the paramagneticstate. The compressibility near van Hove singularity is suppressed most drastically by interaction,while that at low energy (i.e., near the Dirac points) remains close to the noninteracting one,indicating the robustness of the Dirac cone structure. Similarly, the overall phase diagram ofcoupling strength ($U$)-doping plane ($\delta$) is presented.
