Luttinger-liquid phenomenology and angle-resolved photoemission for single-layer Bi₂Sr_{2 − x}La_xCuO_{6 + δ} high-temperature superconductor

Recently observed splitting in angular-resolved photoemission spectroscopy (ARPES) on Bi₂Sr_{2 − x}La_xCuO_{6 + δ} high-temperature superconductor (Janowitz C. et al., Europhys. Lett. 60 (2002) 615) is interpreted within the phenomenological Luttinger-liquid framework, in which both the non-Fermi-liquid scaling exponent of the spectral function and the spin-charge separation are introduced. The anomalous Green function with adjustable parameters fits very well to the Fermi edge and to the low-energy part of ARPES along the Γ-M line in the Brillouin zone. In contrast to one-dimensional models with Luttinger-liquid behavior, we find that both the anomalous scaling α and the parameter δ describing the spin-charge separation are momentum dependent. The higher-energy part of the spectra is not accounted for by this simple Luttinger-liquid form of the Green function. In this energy regime, additional scattering processes are plausible to produce the experimentally observed wide incoherent background, which diminishes as the inverse of the energy.