Broken inversion symmetry in the charge density wave phase in EuAl${}_4$

Abstract

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 $\mathbf{q}\approx 0.17{\mathbf{c}}^{\ast }$. 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 $F222(00\sigma )00s$.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.

10 pages, 7 figures

References in corpus (15)

• Charge density wave orders and enhanced superconductivity under pressure in the kagome metal CsV3Sb5
• Electron-phonon coupling in the charge density wave state of CsV${}_3$Sb${}_5$
• Charge-Density-Wave Order and Multiple Magnetic Transitions in Divalent Europium Compound EuAl${}_4$
• Incommensurate magnetic orders and topological Hall effect in the square-net centrosymmetric EuGa${}_2$Al${}_2$ system
• Rhombic skyrmion lattice coupled with orthorhombic structural distortion in EuAl${}_4$
• Magnetism and charge density waves in RNiC${}_2$ (R = Ce, Pr, Nd)
• Orthorhombic charge density wave on the tetragonal lattice of EuAl4
• Competing charge and magnetic order in the candidate centrosymmetric skyrmion host EuGa${}_2$Al${}_2$
• Charge-density wave transition in magnetic topological semimetal EuAl${}_4$
• Non-centrosymmetric, transverse structural modulation in SrAl4, and elucidation of its origin in the BaAl4 family of compounds
• Real-space Visualization of Charge Density Wave Induced Local Inversion-Symmetry Breaking in a Skyrmion Magnet
• Experimental progress in Eu(Al,Ga)${}_4$ topological antiferromagnets
• Room temperature charge density wave in a tetragonal polymorph of Gd2Os3Si5 and study of its origin in the RE2T3X5 (RE = Rare earth, T = transition metal, X = Si, Ge) series
• I-centered vs F-centered orthorhombic symmetry and negative thermal expansion of the charge density wave of EuAl2Ga2
• Electron-phonon coupling in EuAl4 under hydrostatic pressure

Cited by in corpus (1)

• Origin of multiple skyrmion phases in EuAl4