Nematic susceptibility and quantum oscillations in uniaxially stressed FeSe and LaFePO.

• Applicants: Professor Dr. Jochen Geck; Dr. Clifford Hicks, Ph.D.
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2019 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 429883427

This proposal is to study the stoichiometric iron-based compounds FeSe and LaFePO under strong uniaxial stress, through X-ray structural studies and measurements of quantum oscillations. The goal is two-fold. 1. Can the Poisson’s ratio -dεyy/dεxx, where εxx and εyy are respectively the longitudinal and transverse strains, serve as a measure of nematic susceptibility? At present the elastoresistivity d(ρxx - ρyy)/d(εxx - εyy) is the conventional probe of nematic susceptibility but its analytical usefulness is limited by the fact that resistivity is not a thermodynamic quantity. 2. How do the electronic structures of these compounds evolve under strong uniaxial distortion, that induces or enhances nematic order? This knowledge will help us better untangle the electronic interactions in the unstressed compounds. We propose to hire one student, who will split his or her time approximately equally between TU Dresden and MPI-CPfS.

• DFG Programme: Research Grants