Magnetic fluctuation and dominant superconducting pairing symmetry near the tunable Van Hove singularity

TL;DR

This study explores how magnetic fluctuations and the shape of the density of states near the Van Hove singularity influence superconducting pairing symmetries on a triangular lattice, revealing dominant f-wave pairing near the singularity.

Contribution

It demonstrates how tuning the next-nearest-neighbor hopping parameter affects magnetic correlations and pairing symmetries in the Hubbard model on a triangular lattice.

Findings

Ferromagnetic correlations are enhanced at higher U and β.

f-wave pairing dominates near the Van Hove singularity.

Neither f-wave nor f_n-wave superconductivity is likely near half-filling.

Abstract

We have investigated the magnetism and pairing correlations of the triangular lattice based on the Hubbard model using the determinant quantum Monte Carlo method and the constrained path Monte Carlo. The results show that the presence of the next-nearest-neighbor hopping integral $t^{\prime}$ introduces an additional energy scale to the system, and through $t^{\prime}$, one can regulate the shape of the density of states and thus the position of the van Hove singularity point. Increasing inverse temperature $\beta$ and on-site interaction $U$ favor the formation of ferromagnetic correlation in a rather large filling region, and the calculations for different lattice sizes show that the range of the ferromagnetic correlations is smaller than the smallest lattice simulated at the investigated temperatures. We study the different pairing correlations of the triangular lattice near several typical fillings and show that the $f$-wave pairing dominates the system in the filling region near the van Hove singularity point with a high density of states, where the ferromagnetic correlation is also enhanced. When the filling is close to half-filling, the pairing susceptibility with $f$ wave is suppressed and the pairing susceptibility of $f_n$ wave is enhanced, however, both the effective pairing interaction with $f$ wave and $f_n$ wave are negative, which indicates that neither $f$-wave nor $f_n$-wave superconductivity may exist. Finally, we find that the pairing channel of different symmetry in the system maybe closely related to the magnetic properties. Ferromagnetic fluctuation favors the formation of $f$-wave pairing, while antiferromagnetic fluctuation tends to promote $f_n$-wave pairing.