Antiferromagnetic State in $\hat{I}º$-type Molecular Conductors: Spin Splitting and Mott Gap

Abstract

We numerically investigate the dynamical properties of $\hat{I}º$-type molecular conductors in their antiferromagnetic Mott insulating state. By treating the extended Hubbard model on the two-dimensional $\hat{I}º$-type lattice within the Lanzcos exact diagonalization method, we calculate the one-particle spectral function $A(\mathbf{k},\ddot{I}‰)$ and the optical absorption spectra taking advantage of twisted boundary conditions. We find spin splitting in $A(\mathbf{k},\ddot{I}‰)$ predicted by a previous Hartree-Fock study [M. Naka et al., Nat. Commun. 10, 4305 (2019)]; namely, their up- and down-spin components become different in the general $\mathbf{k}$-points of the Brillouin zone, even without the spin-orbit coupling. Furthermore, we demonstrate the variation in the optical properties near the Mott gap by the presence or absence of the antiferromagnetic order, tuned by a small staggered magnetic field.

5 pages, 3 figures, replaced by the published version