ARPES study of LSCO and PBCO: Electronic structure of the stripe phase and the 1/4-filled Cu-O chains

We have studied the electronic structure of the stripe phase in La_2-xSr_xCuO₄ (LSCO) and the Cu-O chains in PrBa₂Cu₃O₇, (Pr123) and PrBa₂Cu₄0₈ (Pr124) using angle-resolved photoemission spectroscopy (ARPES). In LSCO with x = 0.12, the spectral feature near the Fermi level (E_F) is almost fiat from (π, 0) to (π, π/4), namely, along the stripe direction in LSCO. While the 1/4-filled chain in Pr123 has a band gap because of charge ordering, the metallic chain in Pr124 shows a dispersive feature which reaches E_F at ∼(π, π/4) and a flat feature near E_F which is similar to that observed in the stripe phase of LSCO. Although Pr124 shows spectral-weight suppression near E_F due to the instability toward charge ordering, the suppression is imperfect and Pr124 has a substantial spectral weight at E_F probably due to the chain-chain coupling. This is in sharp contrast to LSC0 with the perfect gap opening near (π, π/4). The difference between the Stripe phase in LSCO and the coupled chains of Pr124 would be derived from the interaction between the stripe and the neighboring Cu spins which suppresses the charge ordering along the stripe.