$d$-wave Superconductivity in the Hubbard model on the isotropic triangular lattice and a possibility of the chiral $d+id$ pairing as a quasi-stable state

A. Yamada

doi:10.7566/JPSJ.94.044705

paper

$d$ -wave Superconductivity in the Hubbard model on the isotropic triangular lattice and a possibility of the chiral $d + i d$ pairing as a quasi-stable state

arXiv:2409.19832 · doi:10.7566/JPSJ.94.044705

Abstract

We study $d$ -wave superconductivity(SC) in the Hubbard model on the isotropic triangular lattice described by the hopping parameter $t$ and on-site Coulomb repulsion $U$ at zero temperature and half-filling using the variational cluster approximation. We found that the $d_{x y}$ SC is the ground state below the Mott insulator phase $U / t ≲ 6$ , and the energy of chiral $d + i d$ SC is slightly higher than the $d_{x y}$ SC. The energy difference between the normal and $d_{x y}$ states is about $0.02 t \sim 0.06 t$ for $U / t ≃ 5$ . This result is semi-quantitatively consistent with the SC transition temperature $T_{K} = 3.9$ K of $I^º$ -(BEDT-TTF) $_{2}$ Cu $_{2}$ (CN) $_{3}$ , where $t$ is estimated to be about $0.06$ eV, and the predicted pairing symmetry $d_{x y}$ agrees with the STM observations. The energy difference between the $d + i d$ and $d_{x y}$ is about $0.01 t \sim 0.03 t$ for $U / t ≃ 5$ so the transition from $d + i d$ to $d_{x y}$ , or some effects of $d + i d$ in $d_{x y}$ phase may be observed in experiments for $I^º$ -(BEDT-TTF) $_{2}$ Cu $_{2}$ (CN) $_{3}$ .

6 pages, 5 figures

d-wave Superconductivity in the Hubbard model on the isotropic triangular lattice and a possibility of the chiral d+id pairing as a quasi-stable state

Abstract

$d$ -wave Superconductivity in the Hubbard model on the isotropic triangular lattice and a possibility of the chiral $d + i d$ pairing as a quasi-stable state