Today electronic, optoelectronic and spintronic technologies are still primarily based on conventional semiconductors and metals, whose electronic structure and dynamics are well studied. While their energy dispersions can be complex, their electronic transport characteristics as well as their optical properties are often understood from textbook electronic band models, and their technological potential has been largely exhausted. In the past few years, novel classes of materials have been identified, which might enable a paradigm shift for future electronics. Many of these materials have in common that their itinerant electrons exhibit (pseudo )relativistic behaviour: in graphene, electrons behave as massless Dirac particles, enabling studies of relativistic phenomena “in a pencil trace”. In topological insulators, the electron spin is locked to the electron momentum, since the relativistic spin-orbit coupling defines the character of the relevant band structure. In novel two-dimensional semiconductors, such as transition metal dichalcogenides, strong spin-orbit coupling locks spin and valley degrees of freedom. Finally, spin-orbit coupling at interfaces, surfaces and in nanostructures influences electrical transport and optics and enables novel topological phenomena. The CRC1277 has successfully explored many fundamental properties of these special electronic band structures as well as the emergent relativistic effects they entail or induce. In the second funding period, we will extend the material basis from individual molecules, graphene, carbon nanotubes, superconductors and topological insulators to novel nanotubes of topological insulators, antiferromagnetic systems, two-dimensional crystals of transition metal dichalcogenides, as well as hybrid structures, functionalized surfaces and interfaces of different material systems. In our well-established highly synergistic theory-experiment collaborations, we will identify how tailored relativistic effects can lead to novel electronic, transport, magnetic and optical properties. Key concepts that will be explored range from spin-orbitronics, valleytronics and antiferromagnetic spintronics, over Majorana fermions to Floquet band engineering and lightwave electronics. Besides steady-state phenomena, our focus on dynamical effects of electrons in pseudo-relativistic band structures, between interfaces and at atomic defects, will be strengthened with new cutting-edge techniques. These include experimentally time-, spin- and angle-resolved photoelectron spectroscopy as well as ultrafast nanoscopy, and the latest theory concepts combining ab-initio methods with Green function-based many-body calculations. Building on the breakthroughs achieved so far, we will exploit Dirac-like band structures and strong spin-orbit coupling to test first examples of optoelectronic, lightwave-electronic and spintronic functionalities.
