Aktuelles Physik-Kolloquium:

11. May. 2017, 16:00 Uhr, Gebäude NW1, Raum H3

Rapid 3D Mapping of Fermi Surface, Fermi Velocity and Spin Texture

Prof. Dr. Gerd Schönhense, Johannes-Gutenberg-Univ. Mainz

The electronic structure of solids is a key element in materials research and –design. All transport and thermodynamical quantities of the electron system of a material depend on the Fermi surface and velocity vF. Band dispersions determine optical and semiconducting properties. A powerful method to study the electronic structure is angular-resolved photoe-mission (ARPES), as described in textbooks (e.g. [1]). In this talk a new way to perform ARPES will be presented, termed momentum microscopy. After a general introduction into photoemission, the new concept will be outlined and its performance illustrated by several examples. High-resolution imaging of the Fourier plane of a cathode lens is combined with time-of-flight (ToF) energy recording, yielding maximal parallelization. The field of view in k-space exceeds the first Brillouin zone, the energy range com-prises several eV. Tunable soft X-rays allow variation of the momentum component perpendicular to the surface via direct transitions to free-electron-like final states. The new approach directly yields the 4D spectral density function (EB;k) (weighted by the photoemission cross section), with 108 resolved data points. Fermi surface and velocity dis-tribution vF(kF) (see figure, from [2]), electron or hole conductivity, effective mass and inner potential can be obtained from p by simple algorithms. An imaging spin filter gives access to the spin texture [3].