Abstract
We study the competition between unconventional superconducting pairing and charge density wave (CDW) formation for the two-dimensional Edwards Hamiltonian at half filling, a very general two-dimensional transport model in which fermionic charge carriers couple to a correlated background medium. Using the projective renormalization method we find that a strong renormalization of the original fermionic band causes a new hole-like Fermi surface to emerge near the center of the Brillouin zone, before it eventually gives rise to the formation of a charge density wave. On the new, disconnected parts of the Fermi surface superconductivity is induced with a sign-changing order parameter. We discuss these findings in the light of recent experiments on iron-based oxypnictide superconductors.
Highlights
We study the competition between unconventional superconducting pairing and charge density wave (CDW) formation for the two-dimensional Edwards Hamiltonian at half filling, a very general twodimensional transport model in which fermionic charge carriers couple to a correlated background medium
We have evaluated the projective renormalization method (PRM) renormalization equations in the half-filled band case, i.e. for Ne/N = 0.5, where Ne is the number of fermionic particles, and have varied the parameter Ω
The second parameter Λ was fixed to a very small value Λ = 0.001 describing a rather stiff, strongly correlated background which supports the formation of ordered states, as for example the SC and CDW states
Summary
We study the competition between unconventional superconducting pairing and charge density wave (CDW) formation for the two-dimensional Edwards Hamiltonian at half filling, a very general twodimensional transport model in which fermionic charge carriers couple to a correlated background medium. A minimal model to effectively describe these interactions considers fermionic charge carriers in the presence of a correlated background that is provided by bosonic modes in the particle’s immediate vicinity which take an active part in the transport of the fermions[9] Such a picture is very general with wide applicability, for example to the case of charge transport in high-temperature SC materials[10,11,12] where superconductivity appears close to magnetically ordered phases[13]. The Edwards model was introduced to describe the motion of a spinless particle in an antiferromagnetic correlated spin background - like a hole in the t-J model In this context the Edwards model is relevant to charge transport in high-temperature superconductors at doping levels close to an antiferromagnetically ordered state[15] and in other materials with related models with spin degrees of freedom[16]. The 2D Edwards Hamiltonian (1) allows the study of superconductivity using spinless fermions and the spin degrees of freedom are modelled by bosons in a way described above
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