Angle-resolved photoemission study of insulating and metallic Cu-O chains in PrBa${}_2$Cu${}_3$O${}_7$ and PrBa${}_2$Cu${}_4$O${}_8$

Abstract

We compare the angle-resolved photoemission spectra of the hole-doped Cu-O chains in PrBa${}_2$Cu${}_3$O${}_7$ (Pr123) and in PrBa${}_2$Cu${}_4$O${}_8$ (Pr124). While, in Pr123, a dispersive feature from the chain takes a band maximum at $k_b$ (momentum along the chain) $\sim$ $\ddot{I}€/4$ and loses its spectral weight around the Fermi level, it reaches the Fermi level at $k_b$ $\sim$ $\ddot{I}€/4$ in Pr124. Although the chains in Pr123 and Pr124 are approximately 1/4-filled, they show contrasting behaviors: While the chains in Pr123 have an instability to charge ordering, those in Pr124 avoid it and show an interesting spectral feature of a metallic coupled-chain system.

4 pages, 5 figures, to be published in PRL