Coexistence and competition of spin-density-wave and superconducting order parameters in iron-based superconductors

Abstract

We theoretically study the coexistence of spin density wave (SDW) and superconductivity (SC) in ironpnictide superconductors based on a three-orbital model, focusing on the momentum-space and real-space distributions of SDW and SC order parameters in the coexistence region. We show that a SDW-SC coexisting state lies in the T-n phase diagram, in qualitative agreement with those of NaFe 1−x Co x As and Ba(Fe 1−x Co x) 2 As 2. In the SC state the pairing wavefunction has s ± symmetry with s x 2 y 2 and s x 2 +y 2 components. In the coexisting state, the SDW and SC order parameters display strong orbital-selective competitions in momentum space, which also result in real-space modulation and spin singlet-triplet mixing in the Cooper pairing amplitude. We expect that the obtained features may be observed in future experiments.

Emergent superconductivity upon disordering a charge density wave ground state

“…Away from the half-filling the DOS has a characteristic two gap structure (being most prominent in the clean system) as shown in Fig. (10). The two gaps arise from the two individual orders as the ground state features both the orders at ρ = 0.95.…”

“…One common feature of nearly all unconventional superconductors is that the superconductivity coexists and competes with other symmetry broken states in a wide range of parameter space. These include the charge orders [1][2][3][4][5][6] and antiferromagnetism [7][8][9] in cuprtate superconductors, spin density waves in pnictides [10][11][12][13], orbital order in Ruthenates [14][15][16], among others. Often, the symmetry unbroken state is accessed via these competing ordered states upon destruction of superconductivity.…”

Orbital driven two-dome superconducting phases in multiorbital superconductors

“…We start from a three-orbital TB model with the NN and NNN exchange interactions and Hund's rule coupling [9,10], which reads…”

“…First of all, the parent compounds of the IBSC are usually bad metals with the magnetic structure of stripe spin-density wave [5], while the undoped cuprates are half-filled antiferromagnetic insulators. Second, the multiorbital or multi-band nature of the IBSC [6][7][8][9][10][11][12][13][14][15][16][17][18][19] is crucially different from the effective singleband nature of the cuprate superconductors [20]. Third, the IBSC are intermediately correlated, with the next-nearest-neighbour (NNN) hoppings and exchanges between iron sites always dominating over the nearest-neighbour (NN) ones [10,[16][17][18][19]; while, the cuprates are strongly short-range correlated, with the NNN hoppings and exchanges much smaller than the NN ones.…”

“…Third, the IBSC are intermediately correlated, with the next-nearest-neighbour (NNN) hoppings and exchanges between iron sites always dominating over the nearest-neighbour (NN) ones [10,[16][17][18][19]; while, the cuprates are strongly short-range correlated, with the NNN hoppings and exchanges much smaller than the NN ones. It leads to a distinct consequence for the SC gap symmetry: the IBSC tend to 56 or 55 wave symmetry [9][10][11][12][13][14][15][16][17][18][19], while the cuprates tend to d wave to reduce the Coulomb repulsion.…”