Superconducting pairing symmetry in the kagome-lattice Hubbard model
Chenyue Wen, Xingchuan Zhu, Zhisong Xiao, Ning Hao, Rubem Mondaini, Huaiming Guo, Shiping Feng
Abstract
The dominating superconducting pairing symmetry of the kagome-lattice Hubbard model is investigated using the determinant quantum Monte Carlo method. The superconducting instability may occur when doping the correlated insulators formed by the Hubbard interaction near the Dirac filling, and the possible superconducting state exhibits an electron-hole asymmetry. Among the pairing symmetries allowed, we demonstrate that the dominating channel is $d$ wave in the hole-doped case. This opens the possibility of condensation into an unconventional ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}+i{d}_{xy}$ phase, which is characterized by an integer topological invariant and gapless edge states. In contrast, the ${s}^{*}$-wave channel, which has no sign change in the pairing function, is favored by the electron doping. We further find the dominating ${s}^{*}$ wave pairing persists up to the Van Hove singularity. The results are closely related to the recent experimental observations in kagome compounds $A{\text{V}}_{3}{\text{Sb}}_{5}(A=\mathrm{K}, \mathrm{Rb}, \mathrm{Cs})$ and provide insight into the pairing mechanism of their superconducting states.