Broken inversion symmetry in the charge density wave phase in EuAl$_4$
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2025
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| _version_ | 1866912640776798208 |
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| author | Kotla, Surya Rohith Noohinejad, Leila Pokhriyal, Preeti Tolkiehn, Martin Agarwal, Harshit Ramakrishnan, Sitaram van Smaalen, Sander |
| author_facet | Kotla, Surya Rohith Noohinejad, Leila Pokhriyal, Preeti Tolkiehn, Martin Agarwal, Harshit Ramakrishnan, Sitaram van Smaalen, Sander |
| contents | EuAl$_4$ exhibits a complex phase diagram, including the development of a charge density wave (CDW) below $T_{CDW} = 145$ K. Below $T_{N}=15.4$ K, a series of antiferromagnetically (AFM) ordered phases appear, while non-trivial 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 $\mathbf{q} \approx 0.17\mathbf{c}^{*}$. 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, non-centrosymmetric orthorhombic or non-centrosymmetric 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 non-centrosymmetric 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 ($2\mathbf{q}$) 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. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2506_01633 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Broken inversion symmetry in the charge density wave phase in EuAl$_4$ Kotla, Surya Rohith Noohinejad, Leila Pokhriyal, Preeti Tolkiehn, Martin Agarwal, Harshit Ramakrishnan, Sitaram van Smaalen, Sander Strongly Correlated Electrons Other Condensed Matter EuAl$_4$ exhibits a complex phase diagram, including the development of a charge density wave (CDW) below $T_{CDW} = 145$ K. Below $T_{N}=15.4$ K, a series of antiferromagnetically (AFM) ordered phases appear, while non-trivial 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 $\mathbf{q} \approx 0.17\mathbf{c}^{*}$. 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, non-centrosymmetric orthorhombic or non-centrosymmetric 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 non-centrosymmetric 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 ($2\mathbf{q}$) 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. |
| title | Broken inversion symmetry in the charge density wave phase in EuAl$_4$ |
| topic | Strongly Correlated Electrons Other Condensed Matter |
| url | https://arxiv.org/abs/2506.01633 |