Optical study of Dirac fermions and related phonon anomalies in the antiferromagnetic compound CaFeAsF
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Xu, Bing
Center for High Pressure Science and Technology Advanced Research, Beijing, China - University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Switzerland
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Xiao, H.
Center for High Pressure Science and Technology Advanced Research, Beijing, China
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Gao, B.
Center for High Pressure Science and Technology Advanced Research, Beijing, China
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Ma, Y. H.
Laboratory of Functional Materials, Chinese Academy of Sciences, Shanghai, China
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Mu, G.
Laboratory of Functional Materials, Chinese Academy of Sciences, Shanghai, China
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Marsik, Premysl
University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Switzerland
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Sheveleva, Evgeniia
University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Switzerland
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Lyzwa, Fryderyk
University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Switzerland
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Dai, Y. M.
Center for Superconducting Physics, Nanjing University, China
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Lobo, R. P. S. M.
LPEM, ESPCI Paris, France - Sorbonne Université, Paris, France
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Bernhard, Christian
University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Switzerland
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Published in:
- Physical Review B. - 2018, vol. 97, no. 19, p. 195110
English
We performed optical studies on CaFeAsF single crystals, a parent compound of the 1111-type iron-based superconductors that undergoes a structural phase transition from tetragonal to orthorhombic at Ts=121 K and a magnetic one to a spin density wave (SDW) state at TN=110 K. In the low-temperature optical conductivity spectrum, after the subtraction of a narrow Drude peak, we observe a pronounced singularity around 300cm−1 that separates two regions of quasilinear conductivity. We outline that these characteristic absorption features are signatures of Dirac fermions, similar to what was previously reported for the BaFe2As2 system [Z.-G. Chen et al., Phys. Rev. Lett. 119, 096401 (2017)]. In support of this interpretation, we show that for the latter system this singular feature disappears rapidly upon electron and hole doping, as expected if it arises from a van Hove singularity in between two Dirac cones. Finally, we show that one of the infrared-active phonon modes (the Fe-As mode at 250cm−1) develops a strongly asymmetric line shape in the SDW state and note that this behavior can be explained in terms of a strong coupling with the Dirac fermions.
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Faculty
- Faculté des sciences et de médecine
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Department
- Département de Physique
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Language
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Classification
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Physics
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License
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License undefined
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Identifiers
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Persistent URL
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https://folia.unifr.ch/unifr/documents/307175
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