Abschlussvortrag im Rahmen des Habilitationsverfahrens

Angle-resolved photoemission spectroscopy (ARPES) measures the interference of dipole allowed Coulomb wavelets from the individual orbital emitters that contribute to an electronic band. If Coulomb scattering of the outgoing electron is neglected, this Huygens view of ARPES simplifies to a Fraunhofer diffraction experiment, and the relevant cross-sections to orbital Fourier transforms. This plane wave approximation (PWA) is surprisingly descriptive of photoelectron distributions but fails to reproduce kinetic energy dependent final state effects like dichroism [1]. Yet, Huygens principle of ARPES can be easily adapted to allow for distortion and phase shift of the outgoing Coulomb wave. This retains the strong physical intuition and low computational cost of the PWA, but naturally captures momentum dependentinterference effects in systems that so far required treatment at the ab initio level, such as hν- dependent ARPES in monolayer graphene [2], linear dichroism in Rashba systems BiAg2 and AgTe, or circular dichroism in the quantum spin Hall insulator indenene [3]. With its remarkable analogy to principles of coherent scattering, it holds enormous potential for a fully coherent ARPES experiment at the diffraction-limited storage rings of the future.

References

[1] S. Moser, J. Electron Spectros. Relat. Phenomena 262, 147278 (2023).
[2] C. S. Kern, A. Haags, L. Egger, X. Yang, H. Kirschner, S. Wolff, T. Seyller, A. Gottwald, M. Richter, U. De Giovannini, A. Rubio, M. G. Ramsey, F. C. Bocquet, S. Soubatch, F. S. Tautz, P. Puschnig, and S. Moser, Phys. Rev. Res. 5, 033075 (2023).
[3] J. Erhardt, C. Schmitt, P. Eck, M. Schmitt, P. Keßler, K. Lee, T. Kim, C. Cacho, I. Cojocariu, D. Baranowski, V. Feyer, L. Veyrat, G. Sangiovanni, R. Claessen, and S. Moser, Phys. Rev. Lett. 132, 196401 (2024).