In-plane electronic anisotropy of differently doped AFe2As2 (A = Ba, Eu) superconductors
Final Report Abstract
We studied the interplay of magnetic and nematic order, superconductivity and the collapsed tetragonal state in the prototypical AFe2As2 (A=Eu, Ca) based iron-pnictides. For EuFe2As2 we found little influence of Eu2+ moments on the electronic properties. However, already very small in-plane magnetic fields act on the configuration of twin domains arising below the tetragonal to orthorhombic phase transition. We found a persistent detwinning by small fields applied below the magnetic ordering of Eu2+ moments which could be quantitatively explained by a minuscule biquadratic coupling between the Eu and Fe magnetic moments, which tries to make the two as parallel as possible. Furthermore, the nature of the collapsed tetragonal state was investigated for Ca0.8Sr0.2Fe2As2. Utilizing synchrotron scattering and spectroscopy for various chemically pressurized single crystals, we found the Fe moments persisting despite the formation of interlayer As–As bonds implying that the Fe-As bond geometry is critical for stabilizing magnetism. Comparison with DFT calculations led us to conclude that the collapsed tetragonal phase is not primarily driven by forming an As-As bond and is instead a nonmagnetic and strongly covalent phase that should be distinguished from other magnetic or paramagnetic phases, even if under certain conditions they have relatively similar lattice parameters.
Publications
- Experimental evidence for importance of Hund’s exchange interaction for incoherence of charge carriers in iron-based superconductors. Phys. Rev. B 95 (2017) 144513
J. Fink, E.D.L. Rienks, S. Thirupathaiah, J. Nayak, A. van Roekeghem, S. Biermann, T. Wolf, P. Adelmann, H.S. Jeevan, P. Gegenwart, S. Wurmehl, C. Felser, and B. Büchner
(See online at https://doi.org/10.1103/PhysRevB.95.144513) - Local and collective magnetism of EuFe2As2. Phys. Rev. B 95 (2017) 115152
Jonathan Pelliciari, Kenji Ishii, Marcus Dantz, Xingye Lu, Daniel E. McNally, Vladimir N. Strocov, Lingyi Xing, Xiancheng Wang, Changqing Jin, Hirale S. Jeevan, Philipp Gegenwart, and Thorsten Schmitt
(See online at https://doi.org/10.1103/PhysRevB.95.115152) - Multistage Magnetic Detwinning in Eu-based Iron Pnictides. Dissertation, Universität Augsburg (2017)
J. Maiwald
- Collapsed tetragonal phase as a strongly covalent and fully nonmagnetic state: Persistent magnetism with interlayer As–As bond formation in Rh-doped Ca0.8Sr0.2Fe2As2. Phys. Rev. B 97 (2018) 020510(R)
K. Zhao, J.K. Glasbrenner, H. Gretarsson, D. Schmitz, J. Bednarcik, M. Etter, J.P. Sun, R.S. Manna, A. Al-Zein, S. Lafuerza, W. Scherer, J.G. Cheng, and P. Gegenwart
(See online at https://doi.org/10.1103/PhysRevB.97.020510) - Microscopic Theory of Magnetic Detwinning in Iron-Based Superconductors with Large-Spin Rare Earths. Phys. Rev. X 8 (2018) 011011
Jannis Maiwald, I.I. Mazin, and Philipp Gegenwart
(See online at https://doi.org/10.1103/PhysRevX.8.011011) - Linkage between scattering rates and superconductivity in doped ferropnictides, arXiv
J. Fink, E.D.L. Rienks, M.Yao, R. Kurleto, J. Bannies, S. Aswartham, I. Morozov, S. Wurmehl, T. Wolf, F. Hardy, C. Meingast, H.S. Jeevan, J. Maiwald, P. Gegenwart, C. Felser, B. Buechner
(See online at https://doi.org/10.1103/PhysRevB.103.155119)
