Würzburg ToCoTronics Colloquium

In recent decades it has become clear that spin-orbit interaction (SOI) should often be considered as more as just a perturbation and is actually responsible for many intriguing physical phenomena. Famous examples of this are Rashba systems and topological materials, which have become important ingredients in the active field of spin-orbitronics. Here I will focus on two there aspects, namely how the functionality of altermagnets relies on SOI and how SOI in materials without spin order can be used to measure intrinsic quantum time scales. For the altermagnets it will be shown how advanced sample preparation techniques allow us to measure the SOI-induced d-wave spin order in MnTe using spin- and angle-resolved photoemission spectroscopy (SARPES). The electronic structure and the sign of the spin polarisation is found to directly depend on the orientation of the altermagnetic Néel vector, providing the first conclusive evidence of the d-wave spin order in the nodal plane, which is responsible for the observed transport phenomena in this novel class of materials. Going to the other extreme, and starting with materials without any spin order in real nor reciprocal space, it will be shown how SARPES can be used to measure the quantum time scale of a transition, without using any external clock. It is found that this attosecond time scale directly depends on the symmetry of bands under investigation, providing a first step to understand the role of time in quantum mechanics and the haute of time in general.