New Developments in Spin-Dependent Photoemission

Abstract

The electron spin governs many phenomena in modern condensed matter physics, such as magnetism, superconductivity, etc. Often, minute details in the electronic structure determine the physical behavior of a material. Photoelectron emission-being the most established approach to explore electronic structures-is currently entering a new era thanks to a breathtaking development in light sources, spectrometer concepts, and spin detectors. In particular, the evolution in novel highly efficient electron spin polarimeters opens up new experimental opportunities and permits unequaled insights into the electronic structure. This contribution will discuss several examples in this field of spin-dependent interactions and spin-based phenomena. A prominent one refers to the class of topological insulators, where strong spin-orbit coupling (SOC) causes a unique spin-momentum locking around the Dirac cone. Transition metal dichalcogenides consist of quasi-2D layers coupled by v. d. Waals interactions. Here, strong SOC leads to pronounced hybridization effects. We also address fundamental issues in ferromagnetism, e.g., the complex interplay of SOC and exchange interaction, causing characteristic k-, spin-and symmetry-dependent band mixing. Using spin-and time-resolved photoemission we explore ultrafast spin dynamics in ferromagnets driven by strong ultrashort laser pulses. We find the changes in both majority and minority spin states to take place on a 100 fs time scale and to be compatible with band mirroring.In this contribution, we will discuss several new aspects of spin-dependent and spin-resolved photoemission covering both static and dynamic issues of electronic states.