Employing high resolution photoemission spectroscopy we show how surface-parallel components of the Fermi vectors can be determined with high accuracy. Intensity modifications due to the photoemission process are explicitly eliminated by comparing photoemission spectra taken at different temperatures. If from one of the other methods a rough estimate is known, the Fermi vector can accurately be fixed by subtracting the photoemission intensities for two temperatures. If taken at the Fermi level for different wave vectors in the neighborhood of the estimate, the vanishing of the difference determines the Fermi vectors. This is valid for a variety of spectral functions, including Lorentzians, Gaussians, Voigt profiles, the Luttinger model, a refined Luttinger profile, two dimensional and marginal Fermi liquids.
Blue bars mark the uncertainties as above.
The intersection with zero marks the Fermi vector. Intensities at the Fermi level are depicted in Fig. 1, top left. The derivative of the energy integrated intensities are depicted in the middle of the left panel. Since the gradient of the integrated intensity is only marginally changing in the regime of interest a rather broad maximum is observed making a detailed quantitative analysis difficult. In the right panel estimates from the peak-tracing method for two assumed profiles are shown.