Ab initio study of superconductivity and inhomogeneity in a Hg-based cuprate superconductor

Abstract

Understanding physics of high-${T}_{c}$ cuprate superconductors remains one of the important problems in materials science. Though a number of diverse theories argue about the superconductivity and competing orders, ab initio and quantitative understanding is lacking. Here, we reproduce the experimental phase diagram of ${\mathrm{HgBa}}_{2}{\mathrm{CuO}}_{4+y}$ by solving its ab initio low-energy effective Hamiltonian without adjustable parameters. It shows a superconducting phase in a wide range of hole density $\ensuremath{\delta}$, and its competition with charge period-4 plus spin period-8 stripe order near $\ensuremath{\delta}\ensuremath{\sim}0.1$, in agreement with experimental results including recent x-ray scattering. Then a crucial role of off-site interactions in stabilizing the superconductivity is elucidated with emphasis on charge fluctuations. It also clarifies the condensation energy mainly contributed from the on-site Coulomb interaction. The present achievement will enable deeper, predictable understanding on open issues of the high-${T}_{c}$ superconducting mechanism and promote ab initio studies on strongly correlated electrons beyond parametrized model studies.