Topology, frustration, and hybridization in quantum matter tuned to extremes and probed by synchrotron radiation

• Applicant: Dr. Marein Rahn
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 501391385

The guided design and manipulation of topologically protected band-inversions, topological magnetism, and superconductivity are the most sought-after advances in quantum materials physics. The recurrent obstacle of such progress is that one cannot easily attribute the mechanisms of novel emergent phenomena to charge, orbital, magnetic, and structural degrees of freedom and their various means of interaction. One strategy to resolve this complexity is to tune the balance between competing terms of a Hamiltonian, observe the impact on order and fluctuations on the relevant scales of momentum and energy, and relate these changes to macroscopic properties. As our abilities to fabricate, manipulate and observe quantum matter are converging on the nanoscale, this approach becomes particularly powerful. While deep insight traditionally required sizable single crystals, experiments at 4th generation light sources will resolve order and fluctuations of correlated electrons "on a chip" and in unprecedented environments. This project aims to utilize such capabilities to address three topical areas, promising first-of-a-kind insights: We will (1) tune magnetic interactions as a means to manipulate topologically protected band-inversions, (2) modify equilibria of competing exchange interactions to stabilize new functional forms of magnetic order and dynamics, and (3) seek material-specific knowledge of the mechanism and relationship of lattice coherence, nematicity and superconductivity. With previous work and demonstrated expertise in each of these fields, the applicant is uniquely qualified to implement this program. Experimentally, the group's main ambition is to drive innovative measurement strategies using resonant x-ray scattering. In particular, we will combine the determination of quantum order and fluctuations with in-situ transport measurements and implement such experiments under extreme pressure, strain, and magnetic fields. These objectives have been aligned with planned developments at several synchrotron beamlines and will be implemented in close collaboration with these facilities. The group will itself develop new instrumentation to access poorly understood phases in the sub-Kelvin / pulsed-field regime. Through seven years of international research, the applicant has built an original scientific portfolio and gained support from a worldwide network of renowned collaborators. In the past two years, he has successfully embedded his goals in the vibrant research environment of Dresden-Concept. Given the interdisciplinary character of this project (combining scattering with transport, nanofabrication and microscopy), the unique density of quantum matter expertise around TU Dresden will be an essential asset. The applicant has already demonstrated strong leadership and interpersonal skills in organizing collaborative efforts of unusual scope, as well as in mentoring and teaching students at all levels.

• DFG Programme: Independent Junior Research Groups
• Major Instrumentation: He-3 cryostat
• Instrumentation Group: 8550 Spezielle Kryostaten (für tiefste Temperaturen)