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Journal Article

Nature of Symmetry Breaking at the Excitonic Insulator Transition: Ta2NiSe5

MPS-Authors
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Windgätter,  L.
International Max Planck Research School for Ultrafast Imaging & Structural Dynamics (IMPRS-UFAST), Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;
Theory Group, Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;

Latini,  S.
Theory Group, Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;

Hübener,  H.
Theory Group, Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;

Rubio,  A.
Theory Group, Theory Department, Max Planck Institute for the Structure and Dynamics of Matter, Max Planck Society;
Center for Computational Quantum Physics, Flatiron Institute, New York;
Nano-Bio Spectroscopy Group, Departamento de Física de Materiales, Universidad del País Vasco;

Fulltext (public)

PhysRevLett.124.197601.pdf
(Publisher version), 2MB

Supplementary Material (public)

suppl_TNS_final.pdf
(Supplementary material), 630KB

Citation

Mazza, G., Rösner, M., Windgätter, L., Latini, S., Hübener, H., Millis, A. J., et al. (2020). Nature of Symmetry Breaking at the Excitonic Insulator Transition: Ta2NiSe5. Physical Review Letters, 124: 197601. doi:10.1103/PhysRevLett.124.197601.


Cite as: http://hdl.handle.net/21.11116/0000-0006-71C9-8
Abstract
Ta2NiSe5 is one of the most promising materials for hosting an excitonic insulator ground state. While a number of experimental observations have been interpreted in this way, the precise nature of the symmetry breaking occurring in Ta2NiSe5, the electronic order parameter, and a realistic microscopic description of the transition mechanism are, however, missing. By a symmetry analysis based on first-principles calculations, we uncover the discrete lattice symmetries which are broken at the transition. We identify a purely electronic order parameter of excitonic nature that breaks these discrete crystal symmetries and contributes to the experimentally observed lattice distortion from an orthorombic to a monoclinic phase. Our results provide a theoretical framework to understand and analyze the excitonic transition in Ta2NiSe5 and settle the fundamental questions about symmetry breaking governing the spontaneous formation of excitonic insulating phases in solid-state materials.