Superconductivity in the Three-Fold Charge-Ordered Metal of the Triangular-Lattice Extended Hubbard Model

TL;DR

This study investigates superconductivity emerging in a three-fold charge-ordered metal within the extended Hubbard model on a triangular lattice, revealing stable triplet f-wave pairing and potential coexistence with charge order at finite temperatures.

Contribution

It derives an effective Hamiltonian for doped carriers in the charge-ordered state and identifies the dominant triplet f-wave pairing symmetry.

Findings

Triplet f-wave pairing is more stable than d_{xy}-wave.

Coexistence of charge order and superconductivity is possible.

Critical temperature for superconductivity is estimated around 0.01 t.

Abstract

The quarter-filling extended Hubbard model on the triangular lattice is studied to explore pairing instability in the three-fold charge-ordered (CO) metal. We derive a second-order strong-coupling effective Hamiltonian of doped carriers into the three-fold CO insulator at electron density of $n=2/3$, and then study the $f$- and $d_{xy}$-wave superconductivities down to $n=1/2$ by using the BCS mean-field approximation. It is found that the triplet $f$-wave pairing is more stable than the $d_{xy}$-wave one. We also point out that this coexisting state of the charge ordering and superconductivity is possible to have critical temperature $T_c \sim 0.01 t$.