Journal Article

PUBDB-2025-03846

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Broken inversion symmetry in the charge density wave phase in EuAl$_4$

Kotla, S. R.Extern*UBT* ; Noohinejad, L.DESY* ; Pokhriyal, P.Extern*DESY* ; Tolkiehn, M.DESY* ; AGARWAL, H.Extern* ; Ramakrishnan, S.Extern* ; van Smaalen, S. (Corresponding author)Extern*UBT*

2025
Inst. Woodbury, NY

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Please use a persistent id in citations: doi:10.1103/kl2z-brms  doi:10.3204/PUBDB-2025-03846

Abstract: EuAl$_4$ exhibits a complex phase diagram, including the development of a charge density wave (CDW) below $T_{\mathrm{CDW}}$ = 145K. Below $T_N$ = 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$_4$ 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$^{∗}$. 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$_4$ 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.

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Contributing Institute(s):

1. FS DOOR-User (FS DOOR-User)
2. Experimentebetreuung PETRA III (FS-PET-D)

Research Program(s):

1. 632 - Materials – Quantum, Complex and Functional Materials (POF4-632) (POF4-632)
2. 6G3 - PETRA III (DESY) (POF4-6G3) (POF4-6G3)
3. FS-Proposal: I-20231047 (I-20231047) (I-20231047)
4. DFG project G:(GEPRIS)406658237 - Aperiodische Kristalle: Struktur, Dynamik und elektronische Eigenschaften (406658237) (406658237)

Experiment(s):

1. PETRA Beamline P24 (PETRA III)

Appears in the scientific report 2025

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Database coverage:
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