Hole-density evolution of the one-particle spectral function in doped ladders

The spectral function A(q,ω) of doped t-J ladders is presented on clusters with up to 2×20 sites at zero temperature applying a recently developed technique that uses up to ∼6×10⁶ rung-basis states. Similarities with photoemission results for the two-dimensional cuprates are observed, such as the existence of a gap at (π,0) near half-filling (caused by hole pair formation) and flat bands in its vicinity. These features should be observable in angle-resolved photoemission spectroscopy experiments on ladders. The main result of the paper is the nontrivial evolution of the spectral function from a narrow band at x=0, to a quasinoninteracting band at x>~0.5. It was also observed that the low-energy peaks of a cluster spectra acquire finite linewidths as their energies move away from the chemical potential.