TRR360 - unsere Mission

More is different, as coined by P.W. Anderson, has been the motto of condensed-matter physics research of the last decades. At each level of complexity, entirely new properties appear. But how to find these new properties in the strange and perplexing quantum world of uncertainty and entanglement? We put forward the new guiding principle, Less is more, inspired by research on geometrically constrained systems, such as 2D electron gas with its astonishing fractionalization of the electric charge – an emergent behavior breaking the conventional paradigm.

Using carefully chosen constraints – intrinsic rather than purely geometrical – we prepare and investigate 3D materials that host novel quantum states. Our research concentrates on the manifestations of constraints in solid-state materials and the practical implementation of these constraints as the way to control quantum states and eventually tailor them to new functionalities.

Our Transregio consortium comprises three research areas that are built around different types of constraints in quantum materials:

Area A makes use of spin-momentum locking to control electron dynamics by magnetic fields, for example in systems with non-trivial band topology. We look for experimental signatures of topological bands – not only electronic but also magnonic – and perform systematic design of magnetic topological materials. We also develop and apply novel experimental tools for understanding complex spin textures in topological magnets.

Area B relies on gauge constraints that restrict spin configurations to extensively degenerate manifolds governed by local rules, such as the two-in-two-out ice rule in pyrochlore magnets. The emergent gauge structures of quantum many-body systems are intimately linked to the long-range entanglement and fractionalization that could be realized and controlled in solid-state settings by implementing gauge constraints in magnetic materials.

Area C takes advantage of the kinetic constraints that lead to peculiar out-of-equilibrium effects, for example when material is pumped into one of its excited states and shows constrained dynamics. We seek to realize new dynamical quantum phases of matter that are not accessible in equilibrium and will serve as a unique probe for emergent quantum phenomena.