Angle-resolved photoemission study of untwinned PrBa2_2Cu3_3O7_7: undoped CuO2_2 plane and doped CuO3_3 chain

We have performed an angle-resolved photoemission study on untwinned PrBa$_2$Cu$_3$O$_7$, which has low resistivity but does not show superconductivity. We have observed a dispersive feature with a band maximum around ($\pi$/2,$\pi$/2), indicating that this band is derived from the undoped CuO$_2$ plane. We have observed another dispersive band exhibiting one-dimensional character, which we attribute to signals from the doped CuO$_3$ chain. The overall band dispersion of the one-dimensional band agrees with the prediction of $t-J$ model calculation with parameters relevant to cuprates except that the intensity near the Fermi level is considerably suppressed in the experiment.Comment: 6 pages, 10 figure