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

The spectral function $A(\mathbf{q},\omega )$ of doped $t-J$ ladders is presented on clusters with up to $2\times 20$ sites at zero temperature applying a recently developed technique that uses up to $\sim 6\times {10}^6$ rung-basis states. Similarities with photoemission results for the two-dimensional cuprates are observed, such as the existence of a gap at $(\pi ,0)$ 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 $x=0\mathrm{}$, 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.