TY  - JOUR
AU  - Kotla, Surya Rohith
AU  - Noohinejad, Leila
AU  - Pokhriyal, Preeti
AU  - Tolkiehn, Martin
AU  - AGARWAL, HARSHIT
AU  - Ramakrishnan, Sitaram
AU  - van Smaalen, Sander
TI  - Broken inversion symmetry in the charge density wave phase in EuAl<sub>4</sub>
JO  - Physical review / B
VL  - 112
IS  - 6
SN  - 2469-9950
CY  - Woodbury, NY
PB  - Inst.
M1  - PUBDB-2025-03846
SP  - 064113
PY  - 2025
AB  - EuAl<sub>4</sub> exhibits a complex phase diagram, including the development of a charge density wave (CDW) below T<sub>CDW</sub> = 145K. Below T<sub>N</sub> = 15.4K, a series of antiferromagnetically (AFM) ordered phases appear, while nontrivial topological phases, like skyrmion lattices, are stabilized under an applied magnetic field. The symmetries of the variously ordered phases are a major issue concerning the understanding of the stabilization of the ordered phases as well as concerning the interplay between the various types of order. EuAl<sub>4</sub> at room temperature has tetragonal symmetry with space group I4/mmm. The CDW phase has an incommensurately modulated crystal structure described by the modulation wave vector q ≈ 0.17 c<sup>∗</sup>. On the basis of various experiments, including elastic and inelastic x-ray scattering, and second-harmonic generation, it has been proposed that the symmetry of the CDW phase of EuAl<sub>4</sub> could be centrosymmetric orthorhombic, noncentrosymmetric orthorhombic or noncentrosymmetric tetragonal. Here, we report temperature-dependent, single-crystal x-ray diffraction experiments that show that the CDW is a transverse CDW with phason disorder, and with noncentrosymmetric symmetry according to the orthorhombic superspace group F222(0 0 σ )00s. Essential for this finding is the availability of a sufficient number of second-order (2q) satellite reflections in the x-ray diffraction data set. The broken inversion symmetry implies that skyrmions might form due to Dzyaloshinskii-Moriya (DM) interactions, instead of a more exotic mechanism as it is required for centrosymmetric structures.
LB  - PUB:(DE-HGF)16
DO  - DOI:10.1103/kl2z-brms
UR  - https://bib-pubdb1.desy.de/record/637354
ER  -