Measuring electronic structure in 4 dimensions – A new approach to photoemission
4th July 2017, COLLOQUIUM, Hörsaal 2, Hörsaalgebäude II, TU Dortmund
Start: 4th July 2017 04:30 p.m.
End: 4th July 2017 00:00
Prof. Dr. Gerd Schönhense, Johannes Gutenberg-Universität Mainz
Prof. Mirko Cinchetti, TU Dortmund University
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. The experimental method of choice is angular-resolved photoemission (ARPES). A new approach to “multidimensional ARPES” (termed momentum microscopy) recently achieved orders of magnitude higher data throughput than conventional ARPES. High-resolution imaging of the Fourier plane of a cathode lens is combined with time-of-flight (ToF) energy recording, yielding maximal parallelization. The (kx,ky)-field of view exceeds the first Brillouin zone, the energy range comprises several eV. Tunable soft X-rays allow variation of kz (perpendicular to the surface) via direct transitions to freeelectron-like final states. This combination of concepts from microscopy and spectroscopy yields the 4D spectral density function r (EB;k) (weighted by the photoemission cross section) with ~108 resolved data points. Fermi surface and velocity distribution vF(kF), all band dispersions, electron or hole conductivity, effective mass and inner potential are obtained from r by simple algorithms. An imaging spin filter gives access to the spin texture.