Cluster dynamical mean field theory of quantum phases on a honeycomb lattice

Abstract

We have studied the ground state of the half-filled Hubbard model on a honeycomb lattice by performing the cluster dynamical mean field theory calculations with exact diagonalization on the cluster-impurity solver. Through using elaborate numerical analytic continuation, we identify the existence of a 'spin liquid' from the on-site interaction U = 0 to Uc (between 4.6t and 4.85t) with a smooth crossover correspondingly from the charge fluctuation dominating phase into the charge correlation dominating phase. The semi-metallic state exits only at U = 0. We further find that the magnetic phase transition at Uc from the 'spin liquid' to the Néel antiferromagnetic Mott insulating phase is a first-order quantum phase transition. We also show that the charge fluctuation plays a substantial role on keeping the 'spin liquid' phase against the emergence of a magnetic order.

Disappearance of the Dirac cone in silicene due to the presence of an electric field

“…The reason for this may be that due to the fact that the CPA is a theory which performs a static average over disorder and hence tends to favour the metallic state [28]. Nevertheless, the presence of an intermediate phase between the semi-metal and Mott insulator such as a spin liquid has been found using both quantum monte carlo (QMC) [29] and cellular dynamical mean-field theory (CDMFT) calculations [30], although the validity of such a result has recently been questioned in the QMC case [31]. Furthermore, the Mott transition value of U c2 ≈ 3.5 obtained in the CPA is in excellent agreement with QMC [32,29,31] and CDMFT calculations [33,34,30].…”

“…Nevertheless, the presence of an intermediate phase between the semi-metal and Mott insulator such as a spin liquid has been found using both quantum monte carlo (QMC) [29] and cellular dynamical mean-field theory (CDMFT) calculations [30], although the validity of such a result has recently been questioned in the QMC case [31]. Furthermore, the Mott transition value of U c2 ≈ 3.5 obtained in the CPA is in excellent agreement with QMC [32,29,31] and CDMFT calculations [33,34,30]. Surprisingly, single-site DMFT calculations yielded values which are much higher than expected [35,36].…”

Correlated Dirac semimetal by periodized cluster dynamical mean-field theory

“…Thus, we calculated the same physical quantities as those by the CDMFT reported in Ref. 9, and then compared them between the PCDMFT and the CDMFT. Specifically, the calculated quantities are the density of states, single-particle gap, staggered magnetization, and double occupancy, respectively shown in the following Figs.…”

“…Following the previous studies [6][7][8][9][10]20 in the literature, we choose a six-site ring as the impurity cluster for the honeycomb lattice, as shown in Fig. 1.…”

Intermediate and spin-liquid phase of the half-filled honeycomb Hubbard model

“…A large number of numerical methods have been applied to study the honeycomb Hubbard model [1][2][3][4]11,[14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. The work by Meng et al used zero-temperature auxiliary-field (determinant) quantum Monte Carlo (AFQMC) [4].…”