Browsing by Author "Stadel, Ryan"

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    Local Orthorhombicity in the Magnetic ${C}_{4}$ Phase of the Hole-Doped Iron-Arsenide Superconductor ${\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{Na}}_{x}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$
    (American Physical Society, 2017) Frandsen, Benjamin A.; Taddei, Keith M.; Yi, Ming; Frano, Alex; Guguchia, Zurab; Yu, Rong; Si, Qimiao; Bugaris, Daniel E.; Stadel, Ryan; Osborn, Raymond; Rosenkranz, Stephan; Chmaissem, Omar; Birgeneau, Robert J.; Rice Center for Quantum Materials
    We report on temperature-dependent pair distribution function measurements of Sr1−xNaxFe2As2, an iron-based superconductor system that contains a magnetic phase with reentrant tetragonal symmetry, known as the magnetic C4 phase. Quantitative refinements indicate that the instantaneous local structure in the C4 phase comprises fluctuating orthorhombic regions with a length scale of ∼2 nm, despite the tetragonal symmetry of the average static structure. Additionally, local orthorhombic fluctuations exist on a similar length scale at temperatures well into the paramagnetic tetragonal phase. These results highlight the exceptionally large nematic susceptibility of iron-based superconductors and have significant implications for the magnetic C4 phase and the neighboring C2 and superconducting phases.
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    Widespread orthorhombic fluctuations in the (Sr,Na)Fe2As2 family of superconductors
    (American Physical Society, 2018) Frandsen, Benjamin A.; Taddei, Keith M.; Bugaris, Daniel E.; Stadel, Ryan; Yi, Ming; Acharya, Arani; Osborn, Raymond; Rosenkranz, Stephan; Chmaissem, Omar; Birgeneau, Robert J.
    We report comprehensive pair distribution function measurements of the hole-doped iron-based superconductor system Sr1−xNaxFe2As2. Structural refinements performed as a function of temperature and length scale reveal orthorhombic distortions of the instantaneous local structure across a large region of the phase diagram possessing average tetragonal symmetry, indicative of fluctuating nematicity. These nematic fluctuations are present up to high doping levels (x≳0.48, near optimal superconductivity) and high temperatures (above room temperature for x=0, decreasing to 150 K for x=0.48), with a typical length scale of 1–3 nm. This work highlights the ubiquity of nematic fluctuations in a representative iron-based superconductor and provides important details about the evolution of these fluctuations across the phase diagram.