Low-energy spin-polarized two-electron spectroscopy: a powerful tool for studying exchange correlation and spin-orbit interaction on surfaces

Abstract

Spin-polarized two-electron spectroscopy-in-reflection has been proven to be a very efficient technique for studying the exchange correlation and spin-orbit interaction on magnetic and non-magnetic surfaces and thin ferromagnetic films. The essence of the technique is the detection of two time-correlated electrons emitted from the sample surface upon an impact of a single incident electron and measurements of their momenta. The coincidence technique has been combined with a time-of-flight electron energy analysis to measure momentum distributions of correlated electron pairs for various orientations of the electron beam polarization relative to the scattering plane and magnetization of the sample. This set of measurements allows to extract the information on exchange correlation and spin-orbit interaction from measured spectra. Energy-and momentum-conservation in the electron-electron scattering allows the valence electron involved into collision to be located in the energy-momentum space of the valence band of the sample. In this way the energy and momentum location of the exchange and SOI can be established. A few examples of the application of this technique for studying ferromagnetic and non-magnetic surfaces are presented.

Spin-orbit effects in two-electron emission from ferromagnetic surfaces

“…20,21 For ferromagnetic surfaces appreciable SOC effects have been found experimentally for an ultrathin Co film on W(110). [22][23][24] While SOC is fairly weak for Co (Z = 27), the substrate W(110) with its large Z = 74 affects the electronic states of the combined system such that the SOC-induced intensity asymmetry A so upon reversal of the spin of the primary electrons reaches about the same size as its exchange-induced counterpart A ex .…”

Controlling spin–orbit interaction in a ferromagnetic Fe/Au double layer

“…An alternative technique, which is very surface sensitive and localizes SOI in energy-momentum space is Low-Energy Spin-Polarized Two-Electron Spectroscopy (SPe,2e). [6][7][8] The essence of two-electron spectroscopy is the detection of two timecorrelated electrons generated by a single incident electron and the measurement of their momenta k 1 and k 2 . The distributions of the correlated electron pairs over the energies of two electrons or over the momenta of the two electrons are called (e,2e) spectra.…”