Angle-resolved photoemission study of the ladder compound Sr14Cu24O41

Angle-resolved photoemission measurements have been performed on Sr14Cu24O41 which consists of two-leg Cu2O3 ladders and edge-sharing CuO2 chains. The data are consistent with the existence of a dispersive band near the Fermi level which has the periodicity of the ladder sublattice. The band shows a minimum binding energy at ka = (2n + 1)pi/2, suggesting that a Mott-Hubbard gap opens on the ladder. The experimental result shows a qualitative agreement with the t-J ladder calculation. It was also found that replacement of Sr with Ca causes a transfer of holes from the chain to the ladder.