Spectral properties and pseudogap in the stripe phases of cuprate superconductors

Using an exact diagonalization method within the dynamical mean-field theory we analyze the stable stripe structures found in the two-dimensional Hubbard model doped by $0.03<\mathrm{}\delta <0.2\mathrm{}$ holes, and discuss a scenario for stripe melting. Our results demonstrate the importance of dynamical correlations which lead to the metallic stripes, in contrast to the Hartree-Fock picture. The spectral functions show a coexistence of the coherent quasiparticles (polaron band) close to the Fermi energy μ, and incoherent states at lower energies. The quasiparticles in the polaron band depend on hole doping, and hybridize strongly with the partly filled mid-gap band within the Mott-Hubbard gap, induced by stripe order. This explains the origin of nondispersive quasiparticles close to the Fermi energy μ, observed near the $X=(\pi ,0)$ and $Y=(0,\pi )$ points for the samples with coexisting (10) and (01) stripes. We reproduce the gap which opens for charge excitations at the $S=(\pi /2,\pi /2)$ point, observed in the angle-resolved photoemission experiments for ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x{\mathrm{CuO}}_4,$ and a pseudogap in the integrated spectral density pinned to μ. Finally, we show that large spectral weight close to $\mu$ moves from the X to the S point when the second neighbor hopping element increases, and the (01) stripe phase is destabilized by kink fluctuations.