# Infrared study of the spin reorientation transition and its reversal in the superconducting state in underdoped ${\mathrm{Ba}}_{1-x}{\mathrm{K}}_{x}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$

• Mallett, B. P. P. University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Fribourg, Switzerland
• Maršík, Premysl University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Fribourg, Switzerland
• Yazdi-Rizi, M. University of Fribourg, Department of Physics and Fribourg Center for Nanomaterials, Fribourg, Switzerland
08.07.2015
Published in:
• Physical Review Letters. - 2015, vol. 115, no. 2, p. 027003
English With infrared spectroscopy we investigated the spin-reorientation transition from an orthorhombic antiferromagnetic (o-AF) to a tetragonal AF (t-AF) phase and the reentrance of the o-AF phase in the superconducting state of underdoped Ba1−xKxFe2As2. In agreement with the predicted transition from a single-Q to a double-Q AF structure, we found that a distinct spin density wave develops in the t-AF phase. The pair breaking peak of this spin density wave acquires much more low-energy spectral weight than the one in the o-AF state which indicates that it competes more strongly with superconductivity. We also observed additional phonon modes in the t-AF phase which likely arise from a Brillouin-zone folding that is induced by the double-Q magnetic structure with two Fe sublattices exhibiting different magnitudes of the magnetic moment.
Faculty
Faculté des sciences et de médecine
Department
Département de Physique
Language
• English
Classification
Physics