1 research outputs found
Orbital-Selective Superconductivity and the Effect of Lattice Distortion in Iron-Based Superconductors
The superconducting (SC) state of iron-based compounds in both tetragonal and
orthorhombic phases is studied on the basis of an effective Hamiltonian
composed of the kinetic energy including the five Fe 3d-orbitals, the
orthorhombic crystalline electric field (CEF) energy, and the two-orbital
Kugel'-Khomski\u{i}-type superexchange interaction. Our basic assumption is
that the antiferromagnetic (AF) state in the parent compounds can be described
by the and orbitals, and that the electrons in these orbitals
have relatively strong electron correlation in the vicinity of the AF state. In
order to study the physical origin of the structure-sensitive SC transition
temperature, the effect of orthorhombic distortion is taken into account as the
energy-splitting, , between the and
orbitals. We find that the eigenvalue of the linearized gap equation decreases
accompanied with the reduction of the partial density of states for the
and orbitals as increases, and
that the dominant pairing symmetry is an unconventional fully gapped
-wave pairing. We also find large anisotropy of the SC gap function in
the orthorhombic phase. We propose that the CEF energy plays an important role
in controlling and the SC gap function, and that
orbital-selective superconductivity is a key feature in iron-based
superconductors, which causes the structure-sensitive .Comment: 11 pages, To appear in J. Phys. Soc. Jp