Detail:
Abstract: Understanding the origin of high temperature (high-Tc ) superconductivity in cuprates and iron-based superconductors remains one of the most challenging problems in condensed matter physics. Here we discuss the relationship among global electronic structures, local structural building blocks and electron occupation numbers in these two classes of materials and show that both of them host a special common electronic environment in which the 3d-orbitals with the strongest antiferromagnetic superexchange coupling are isolated near Fermi energy to produce high-Tcsuperconductivity. This environment characterizes the gene of high temperature superconductivity, which can help us to identify new candidates of high-Tc superconductors. A specific prediction on the candidacy was made in materials with a two-dimensional hexagonal lattice constructed by corner-shared trigonal-bipyramidal complexes with a d7 filling configuration at the cation sites. Such a lattice structure has been observed in Mn- and Fe-based compounds. However, realizing a d7 filling configuration requires Co2+ or Ni3+ 3d transition metal cation ions. The new materials, if synthesized, was predicted to host superconducting states with a d+id pairing symmetry, and their maximum Tc is expected to exceed those of iron-based superconductors. Their prediction, if confirmed, can pave the way for discovering new classes of high-Tc superconductors to settle the debate about unconventional high-Tc superconducting mechanisms.
