Exotic Physics in Mott insulators

 

In recent decades there have been great advances in understanding the topological properties of weakly interacting electrons. However, much less is known for strongly interacting fermionic systems, like the Mott insulators. In these insulators magnetic moments interact with each other, realizing new states of quantum matter with exotic excitations and unusual ground state properties. What new phenomena may we expect, especially if we consider the coupling between spins, lattice, and electric polarization due to spin-orbit coupling? 

 

 For example, the Hall effect in metals a consequence of the electronic bands having a finite Chern number. In the insulators there are no conducting electrons, but may it happen that a kind of dynamical Hall effect emerges at finite excitation energies, which can be observed by light absorption in the SrCu₂(BO₃)₂?  

 

What are the properties of spin excitations in multi-layered CrI₃? Is it possible to observe spin-quadrupolar excitations in materials suspected to realize spin-nematic ordering, like LiCuVO₄? 

 

Going beyond ordered materials, does the magnetoelectric effect leads to new physics in spin liquids? 

 

In this Ph.D. project, we will aim to address such questions. This is a theoretical study requiring the application of analytical and numerical methods, with the possibility to interact with experimental groups of Profs. S. Bordács and F. Simon.