Determinantal quantum Monte Carlo study of pairing instabilities on the honeycomb lattice

Tianxing Ma

Milan ˇ Zukovič

Chao Wang, Yoni Schattner, Steven Allan Kivelson

Tao Ying, Stefan Weßel

Using finite-temperature determinantal quantum Monte Carlo calculations, we reexamine the pairing susceptibilities in the Hubbard model on the honeycomb lattice, focusing on doping levels onto and away from the Van Hove singularity (VHS) filling. For this purpose, electronic densities of 0.75 (at the hole-doping VHS) and 0.4 (well below the VHS) are considered in detail, where due to a severe sign problem at strong coupling strengths, we focus on the weak-interaction region of the Hubbard model Hamiltonian. By analyzing the temperature dependence of pairing susceptibilities in various symmetry channels, we find the singlet $d+id$ wave to be the dominant pairing channel both at and away from the VHS filling. We furthermore investigate the electronic susceptibility to a specific chiral spin density wave (SDW) order, which we find to be similarly relevant at the VHS, while it extenuates upon doping away from the VHS filling.

Carsten Honerkamp A

Kean Loon Lee, Karim Bouadim, G. G. Batrouni +4 more

We study the attractive fermionic Hubbard model on a honeycomb lattice using determinantal quantum Monte Carlo simulations. By increasing the interaction strength $U$ (relative to the hopping parameter $t$) at half filling and zero temperature, the system undergoes a quantum phase transition at $5.0<{U}_{c}/t<5.1$ from a semimetal to a phase displaying simultaneously superfluid behavior and density order. Doping away from half filling, and increasing the interaction strength at finite but low temperature $T$, the system always appears to be a superfluid exhibiting a crossover between a BCS and a molecular regime. These different regimes are analyzed by studying the spectral function. The formation of pairs and the emergence of phase coherence throughout the sample are studied as $U$ is increased and $T$ is lowered.