Abstract

By using a photoelectron emission microscope (PEEM) we commonly look at strongly magnified images of a sample's surface in real space. Likewise, a momentum microscope utilizes the principles of electron microscopy to form a high resolution image of the distribution of electronic states in reciprocal (i.e., momentum-) space [1]. Such two- dimensional (kx,ky) maps of the photoelectron distribution represent sections through the valence electronic states in the full surface Brillouin zone, and give a comprehensive and intuitive access to the electronic properties of a material. Together with advanced time-of- flight (ToF) detection schemes the full band information becomes available within minutes.

Of particular importance is the spin of the electron, that gives rise to phenomena like ferromagnetism, superconductivity, spin-polarized surface states, and recently, the discovery of new material classes with complex spin textures like topological insulators. With the introduction of imaging spin analyzers [2] the efficiency of spin-resolved measurements experienced a tremendous boost, such that the electron spin now becomes routinely accessible in a photoemission experiment.

We will discuss applications and prospects, including spin-textures of topological materials [3], spin-orbit- and exchange-interaction in ferromagnets [4], and rapid band structure mapping by multi-MHz ToF momentum microscopy [5]. The results pave the way to comprehensive 3D band mapping with complete wave-vector-, spin-, and time-resolution at next generation light sources.

References

[1] C. Tusche, A. Krasyuk, J. Kirschner, Ultramicroscopy 159, p. 520 (2015)

[2] C. Tusche, M. Ellguth, A. A. Ünal, C.-T. Chiang et al., Appl. Phys. Lett. 99, 032505 (2011) [3] H. Maaß, H. Bentmann, C. Seibel, C. Tusche et al., Nat. Commun. 7, 11621 (2016)

[4] M. Ellguth, C. Tusche, J. Kirschner, Phys. Rev. Lett., 115, 266801 (2015)

[5] C. Tusche, P. Goslawski, D. Kutnyakhov, M. Ellguth et al., Appl. Phys. Lett. 108, 261602 (2016)