Figure 3: Anisotropic Fermi liquid properties

(a) Fermi liquid cutoff energy ω_c derived from momentum distribution analysis (Fig. 2) and plotted vs Fermi surface angle φ. The error bars are the precision with which ω_c can be determined from Γ_k vs ω (see supplementary Fig. S4). The applied energy resolution is indicated in the lower left corner. In the shaded area above ω_c, an approximately linear ω-dependence is observed. This region is limited either by the bottom of the valence band or by an interaction cutoff ²¹. (b) , where β₂ is obtained from the momentum distribution linewidth ΔΓ=β₂ω² and v_k is the bare-band Fermi velocity ²⁶ (see also supplementary Table S1 and the method section), as a function of φ. The error bars indicate the standard deviation related to the determination of β₂. (c) Electron–electron coupling constant λ derived from a and b and plotted against Fermi surface angle. The error bars are derived from those shown in panels a and b. The inset shows schematically the ‘Fermi surface’ consisting of nodal Fermi arcs (blue) where true Fermi liquid quasiparticle excitations are found and the sections with non-Fermi liquid excitations (red). Vertical dashed lines indicate φ₀ – the Fermi surface angle where ω_c→0. All other dashed lines are guides to the eye.