Calculated phase diagram of doped BaFe₂As₂ superconductor in a C₄-symmetry breaking model

¹ Department of Physics, University of Houston - Houston, TX 77004, USA
² Theoretical Division, Los Alamos National Laboratory - Los Alamos, NM 87545, USA
³ Center for Integrated Nanotechnologies - Los Alamos, NM 87545, USA

Received: 12 September 2013
Accepted: 13 September 2013

Abstract

We develop a minimal multiorbital tight-binding model with realistic hopping parameters. The model breaks the symmetry of the tetragonal point group by lowering it from C₄ to D_2d, which accurately describes the Fermi surface evolution of the electron-doped BaFe_2−xCo_xAs₂ and hole-doped Ba_1−yK_yFe₂As₂ compounds. An investigation of the phase diagram with a mean-field Bogoliubov-de Gennes Hamiltonian results in agreement with the experimentally observed electron- and hole-doped phase diagram with only one set of t, U and V parameters. Additionally, the self-consistently calculated superconducting order parameter exhibits -wave pairing symmetry with a small d-wave pairing admixture in the entire doping range, which is the subtle result of the weakly broken symmetry and competing interactions in the multiorbital mean-field Hamiltonian.