Laser-Enhanced Single Crystal Growth of Non-Symmorphic Materials: Applications to an Eight-Fold Fermion Candidate

Materials with nonsymmorphic symmetries have many applications and have recently come to the forefront as possibly harboring new topological states of matter, such as 8-fold fermions. Here, we report the single crystal growth of Bi₂CuO₄ using the traveling solvent floating zone technique. Using laser heating combined with a 0.875 Bi₂CuO₄:0.125 Bi₂O₃ solvent, we produce untwinned single crystal pieces. Three-dimensional X-ray microcomputed tomography is used to probe the fundamental origins of twinning, grain formation, and growth. Powder X-ray diffraction and Laue diffraction show that Bi₂CuO₄ crystallizes in the space group P4/ncc (#130), orders antiferromagnetically with T_N = 43 K, and, combined with comparisons to the literature, demonstrate the crystallinity and reproducibility of the synthesis. The entropy lost at the magnetic phase transition is ΔS_mag = 0.25 ln(2); it arises from a high anisotropy in the magnetic interactions. We carry out a symmetry analysis demonstrating that Bi₂CuO₄’s magnetic order implies a rich breaking of the parent 8-fold symmetric states. Our results provide a roadmap for the creation of future magnetic derivatives of 8-fold, double Dirac single crystals and related quantum states of matter with nonsymmorphic symmetries. This approach also offers guidance on improving the single growth of nonsymmorphic materials from cuprates to van der Waals solids.