In-situ handles on topology and correlations in quantum matter

The goal of this PhD project is to clarify the hierarchy of correlation mechanisms and the role of topology in strongly correlated electron systems. It is now well known that many of the most topical emergent quantum phenomena are intertwined with lattice instabilities and depend crucially on the implied changes of crystalline symmetry [1]. However, in many cases it has been a great challenge to conclusively link the bulk emergent physical properties to structural and magnetic variations on atomic scales of energy and momentum. Such knowledge is often the missing link to enable bottom-up explanations of the underlying correlation mechanisms.

The strategy of this project will be to tune the lattices of topological band materials and superconductors [2,3] by external tuning parameters [4], and then to characterize the response both on the macro- and on the microscopic (atomic) scale. To bridge this gap, the project is designed as a collaboration between two groups of complementary experimental expertise.

In the first part of the project, the candidate will work with Dr. Elena Gati (MPI CPfS) to develop expertise in thermal and transport measurements under pressure and strain. Once measurements on model materials have been successfully implemented, the candidate will work with Dr. Marein Rahn (IFMP, TUD) to correlate their observations with insights from x-ray scattering. This includes the characterization of subtle structural/charge ordering instabilities, of magnetic structures, and of the dispersions of the associated elementary fluctuations.

To address structural and charge degrees of freedom, the candidate will first learn to plan and perform experiments on state-of-the-art custom-built x-ray diffractometers at TUD. Once these experiments are well established, corresponding studies of magnetic or orbital order and fluctuations will be implemented at synchrotron facilities worldwide. For certain materials, it will be of special interest to establish in-situ approaches that combine charge transport and resonant x-ray scattering in the same experiment.