Dispersion of ordered stripe phases in the cuprates

A phase-separation model is presented for the stripe phase of the cuprates, which allows the doping dependence of the photoemission spectra to be calculated. The idealized limit of a well-ordered array of magnetic and charged stripes is analyzed, including effects of long-range Coulomb repulsion. Remarkably, down to the limit of two-cell-wide stripes, the dispersion can be interpreted as essentially a superposition of the two end-phase dispersions, with superposed minigaps associated with the lattice periodicity. The largest minigap falls near the Fermi level; it can be enhanced by proximity to a (bulk) van Hove singularity. The calculated spectra are dominated by two features: this charge stripe minigap plus the magnetic stripe Hubbard gap. There is a strong correlation between these two features and the experimental photoemission results of a two-peak dispersion in ${\mathrm{La}}_{2-x}{\mathrm{Sr}}_x{\mathrm{CuO}}_4$ and the peak-dip-hump spectra in ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }.$ The differences are suggestive of the role of increasing stripe fluctuations. The 1/8 anomaly is associated with a crossover from magnetic-dominated to charge-dominated stripes. A model is proposed for the limiting minority magnetic phase as an isolated two-leg ladder.