Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 13: Electronic Structure of Surfaces II

O 13.1: Hauptvortrag

Montag, 16. März 2015, 15:00–15:30, MA 041

Advanced spin-resolved momentum microscopy — •Christian Tusche — Max-Planck-Institut für Mikrostrukturphysik, Halle, Germany

Angle resolved photoemission spectroscopy (ARPES) is an universal tool to probe the electronic structure of solids. Conventional electron spectrometers measure the distribution of photoelectrons in a limited angular interval, which makes complete mapping of band structures a time consuming task. Here, we discuss the recent approach to this issue by momentum microscopy. A momentum microscope captures the complete 2π solid angle of emission directions into a high resolution (k_x, k_y) image of the full surface Brillouin zone of a solid. This efficient measurement scheme intrinsically provides comprehensive quantitative information beyond high-symmetry directions.

Of particular importance is the spin of the electron, that gives rise to phenomena like ferromagnetism, spin-polarized surface states, and the discovery of new material classes like topological insulators. So far, however, the spin was only inefficiently probed in photoemission experiments, resulting in a rather low figure of merit (10⁻⁴) for spin-resolved ARPES. This longstanding problem is defeated by introducing the novel concept of spin-resolved momentum microscopy: In combination with an imaging spin filter, we measure more than 5000 spin-resolved points in the full k_||-space, simultaneously. We will discuss examples ranging from the spin-resolved Fermi surface of ferromagnets to highly polarized states in topological insulators.