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Scientists conducting experimental and theoretical studies of Iron Pnictides through Zero Field Nuclear Magnetic Resonance

Karen Sauer, Professor, Physics and Astronomy, and Igor Mazin, Professor of Practice for Advanced Studies in Theoretical Physics, Quantum Science and Engineering Center (QSEC), Physics and Astronomy, are set toreceive funding from the National Science Foundation for the project: "Experimental and theoretical studies of iron pnictides through zero field nuclear magnetic resonance." 

For this project, the researchers will study phase transitions between magnetic and nematic long-range ordered phases, as well as phases without either orders or with a yet unknown (“hidden”) order in iron-based high-temperature superconductors (FeBS), using zero-field nuclear magnetic resonance (NMR). NMR is a tool of choice for probing internal magnetic and electric fields. The former is key to understand the magnetic ordering; the latter for understanding the charge density.   

Further, the NMR relaxation rates reveal dynamics that happen on slower time-scales; the particular interest here is the transition between different types of ordered and strongly fluctuating states. Most NMR experiments are done at high magnetic fields for ease of experimentation, but then many effects of interest are only perturbations to the dominant Hamiltonian.  

The researchers propose to study instead a regime in which the hyperfine field and the electric quadrupole field are not perturbations, but uniquely determine the NMR signal. Their ultimate goal is to understand the physics of magnetic and especially nematic fluctuations, which are generally believed to be a key to the unique superconducting properties of FeBS. 

The researchers will receive $560,673 from NSF for this project. Funding will begin in Sept. 2022 and will end in late Aug. 2025.