Unconventional superconductivity on the triangular lattice Hubbard model

Abstract

Using large-scale dynamical cluster quantum Monte Carlo simulations, we explore the unconventional superconductivity in the hole-doped Hubbard model on the triangular lattice. Due to the interplay of electronic correlations, geometric frustration, and Fermi surface topology, we find a doubly degenerate singlet pairing state at an interaction strength close to the bare bandwidth. Such an unconventional superconducting state is mediated by antiferromagnetic spin fluctuations along the $\hat{I}“$-$K$ direction, where the Fermi surface is nested. An exact decomposition of the irreducible particle-particle vertex further confirms the dominant component of the effective pairing interaction comes from the spin channel. Our findings provide support for chiral $d+id$ superconductivity in water-intercalated sodium cobaltates Na${}_x$CoO${}_2\cdot y$H${}_2$O, as well as insight into the superconducting phases of the organic compounds $\hat{I}º$-(ET)${}_2$X and Pd(dmit)${}_2$.

5 pages, 4 figures