Electronic structure of a dual-layered organic charge transfer salt*

We examine the electronic properties of polymorphs of (BEDT-TTF)$_2$Ag(CF$_3$)$_4$(TCE) (1,1,2-trichloroethane) within density functional theory (DFT). While a phase with low superconducting transition temperature $T_c=2.6$~K exhibits a $\kappa$ packing motif, two high $T_c$ phases are layered structures consisting of $\alpha'$ and $\kappa$ packed layers. We determine the electronic structures and discuss the influence of the insulating $\alpha'$ layer on the conducting $\kappa$ layer. We find that the stripes of high and low charge in the $\alpha'$ layer correspond to a stripe pattern of hopping parameters in the $\kappa$ layer. This finding is the basis for studying the effect of the different underlying Hamiltonians on the superconducting properties.