Orbital-resolved vortex-core states in FeSe superconductors: A calculation based on a three-orbital model

Abstract

We study electronic structure of vortex core states of FeSe superconductors based on a t2g threeorbital model by solving the Bogoliubov-de Gennes(BdG) equation self-consistently. The orbitalresolved vortex core states of different pairing symmetries manifest themselves as distinguishable structures due to different quasi-particle wavefunctions. The obtained vortices are classified in terms of the invariant subgroups of the symmetry group of the mean-field Hamiltonian in the presence of magnetic field. Isotropic s and anisotropic s wave vortices have G5 symmetry for each orbital, whereas d x 2 −y 2 wave vortices show G * 6 symmetry for d xz/yz orbitals and G * 5 symmetry for dxy orbital. In the case of d x 2 −y 2 wave vortices, hybridized-pairing between dxz and dyz orbitals gives rise to a relative phase difference in terms of gauge transformed pairing order parameters between d xz/yz and dxy orbitals, which is essentially caused by a transformation of co-representation of between d xz/yz and dxy orbital-resolved d x 2 −y 2 wave vortices can be verified by further experiment observation.

Effects of carrier density and interactions on pairing symmetry in a t2g model

“…The superconducting pairing symmetry of the latter group has been extensively studied across a broad range of doping levels (from electron to hole doping) in the context of iron-based superconductivity. [48][49][50][51][52][53][54] In contrast, the evolution of superconducting pairing symmetry with electron concentrations in the former group has not been explored, as Sr 2 RuO 4 only involves a fixed electron concentration. Investigating the electron-density dependence of the pairing symmetry in the related model will help supplement our understanding of the superconducting mechanism in the d-orbital systems.…”

Signatures of nodeless multiband superconductivity and particle-hole crossover in the vortex cores of FeTe0.55Se0.45

“…Because of this, a tempting interpretation of the experimental data would be that vortices show a mixture of electron-like and hole-like bound states. Motivated by measurements on pnictides, a number of authors have studied vortices in models featuring electron and hole bands [13,[15][16][17][18][19][20][21]. A comparison with FeTe 0.55 Se 0.45 is difficult, as these works either choose parameters not in the quantum regime, or use exact diagonalization on small systems and fail to achieve the high energy resolution required in order to address discrete vortex levels.…”