Numerical Study of a Multiorbital Hubbard Model for the Two-Leg Ladder BaFe$_{2}$S$_{3}$ High-Tc Superconductor Using the Density Matrix Renormalization Group

Iron based high-Tc superconductors have attracted considerable attention because of its unconventional superconducting properties. Here, we analyze the magnetic and pairing characteristics of the recently discovered two-leg ladder material BaFe$_{2}$S$_{3}$ that becomes superconducting by applying pressure [1], using a two-orbital Hubbard model studied via the Density Matrix Renormalization Group technique. The hopping parameters, which spans up-to the $2^{nd}$ nearest-neighbor rungs, were obtained from the ab-initio downfolded band structure at ambient and high pressures [2]. The magnetic phase diagram at a realistic Hund coupling $J/U = 0.25$ is presented varying the Hubbard $U$, at select values of the electronic fillings. At half-filling, we find a robust magnetic order in excellent agreement with experiments [1] i.e. antiferromagnetic (ferromagnetic) along the leg (rung) directions. We also discuss a possible tendency for this system to form a paired bound state of holes in a small but finite window of Hubbard $U$. The symmetries of this tentative paired ground state will be discussed. \\[4pt] [1] Hiroki Takahashi et al., \textit{Nature Materials \textbf{14}, 1008 (2015)}\\[0pt] [2] Ryotaro Arita et al., \textit{Phys. Rev. B \textbf{92}, 054515 (2015)}