Photoelectron spectroscopy in a wide hν region from 6 eV to 8 keV with full momentum and spin resolution

Abstract

High resolution photoelectron spectroscopy is recognized to be a very powerful approach to study surface and bulk electronic structures of various solids by employing different photon energies (hν). In particular, angle resolved photoelectron spectroscopy (ARPES) has progressed dramatically in the last few decades providing useful information on Fermi surface (FS) topology and band dispersions.The information of the electron spin is often decisive to fully understand the electronic properties of many material classes. However, spin-resolved studies by photoelectron spectroscopy were strongly hindered by the low detection efficiency of spin detectors. In the case of surface electronic structures, possible surface degradation with time is a serious problem to discuss intrinsic electronic effects. Therefore rather fast and high efficiency detection is required in the case of surface sensitive spin-resolved ARPES.Two-dimensional (2D) detection is nowadays widely employed in ARPES. In the use of a conventional hemispherical deflection analyzer (HDA), one direction on the 2D detector corresponds to the binding energy EB and the other direction to the emission angle. The novel concept of momentum microscopy, however, directly provides 2D (kx,ky) maps of the photoemission intensities. The reciprocal space image directly represents the cross section through the valence band structure of the sample at a selected energy. By scanning EB, very high resolution three-dimensional EB(kx,ky) maps of the band-dispersion can be obtained with high efficiency.If combined with a 2D imaging spin filter, based on electron reflection at a Au/Ir(001) surface, spin detection efficiency with orders of magnitude higher than other spin detectors is realized, opening a breakthrough in spin-resolved ARPES (SP-ARPES).