Pseudogap behaviour in Bi2212: Results of Generalized DMFT Approach
  To describe pseudogap regime in Bi2212 we employ novel generalized ab initio LDA+DMFT+Sigma_k hybrid scheme. This scheme is based on the strategy of one of the most powerfull computational tool for real correlated materials LDA+DMFT. Here the LDA+DMFT equations are supplied by an additional (momentum dependent) self-energy Sigma_k in the spirit of our recently proposed DMFT+Sigma_k approach, accounting for pseudogap fluctuations. In the present model Sigma_k describes non-local correlations induced by short-ranged collective Heisenberg-like antiferromagnetic spin fluctuations. The effective single impurity problem of the DMFT is solved by NRG. Material specific model parameters for effective x2-y2 orbital of Cu-3d shell of Bi2212 compound, e.g. hopping integrals, local Coulomb interaction U and pseudogap potential Delta were obtained within LDA and LDA+DMFT. We report theoretical LDA+DMFT+Sigma_k quasiparticle bands dispersion and damping, Fermi surface renormalization, momentum anisotropy of (quasi) static scattering, densities of states, spectral densities and angular resolved photoemission (ARPES) spectra accounting for pseudogap and bilayer splitting effects for normal (slightly) underdoped Bi2212 (delta=0.15). We show that LDA+DMFT+Sigma_k successfully describes strong (pseudogap) scattering close to Brillouin zone boundaries. Our calculated LDA+DMFT+Sigma_k Fermi surfaces and ARPES spectra in presence of the pseudogap fluctuations are almost insensitive to the bilayer splitting strength. The LDA-calculated value of bilayer splitting is found to be rather small to describe experimentally observed peak-dip-hump structure. 
E.Z.Kuchinskii, I.A.Nekrasov, Z.V.Pchelkina, M.V.Sadovskii