Photoemission in the system of linear chains : application to PrBa$_2$Cu$_3$O$_7$ and La$_{\rm 2-x-y}$Nd$_{\rm y}$Sr$_{\rm x}$CuO$_4$

Abstract

Photoemission in the system of linear charged chains has been studied with the dipole matrix incorporated, from which its dependencies on the photoelectron momentum (${\bf k}$), photon polarization ($\hat{\bf E}$), and photon energy ($ω$) can be explored. The used model is the three-dimensional array of noninteracting chains, which is so simple as to allow an analytic approach. Motivations of the study are for the doped CuO$_3$ chain in PrBa$_2$Cu$_3$O$_7$ and the doped static stripe phase in La$_{\rm 2-x-y}$Nd$_{\rm y}$Sr$_{\rm x}$CuO$_4$. The one-dimensional dispersion exhibiting spin-charge separation and its dependence on the momentum perpendicular to the chain and its $\hat{\bf E}$-dependency as well are discussed in PrBa$_2$Cu$_3$O$_7$. For La$_{\rm 2-x-y}$Nd$_{\rm y}$Sr$_{\rm x}$CuO$_4$, the anomalous spectral distribution formed by two sets of stripes perpendicular to each other is investigated. The geometric effects led to by the dipole transition matrix including the interference of photocurrents from different chains are found to change the simple one-dimensional feature drastically. We find these changes are consistent with experiment for the chain system PrBa$_2$Cu$_3$O$_7$, but less satisfactory for the stripe phase in La$_{\rm 2-x-y}$Nd$_{\rm y}$Sr$_{\rm x}$CuO$_4$. This means that in the stripe phase much two-dimensional characters still exist unlike the chain system.