First-principles study of the low-temperature charge density wave phase in the quasi-one-dimensional Weyl chiral compound <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>(</mml:mo><mml:mrow><mml:msub><mml:mi>TaSe</mml:mi><mml:mn>4</mml:mn></mml:msub><mml:msub><mml:mrow><mml:mo>)</mml:mo></mml:mrow><mml:mn>2</mml:mn></mml:msub><mml:mi mathvariant="normal">I</mml:mi></mml:mrow></mml:math>
Yang Zhang, Ling-Fang Lin, Adriana Moreo, Shuai Dong, Elbio Dagotto
Abstract
Using ab initio density functional theory, we study the lattice phase transition of quasi-one-dimensional $({\mathrm{TaSe}}_{4}{)}_{2}\mathrm{I}$. In the undistorted state, the strongly anisotropic semimetal band structure presents two nonequivalent Weyl points. In previous efforts, two possible Ta-tetramerization patterns were proposed to be associated with the low-temperature structure. Our phonon calculations indicate that the orthorhombic $F222$ CDW-I phase is the most likely ground state for this quasi-one-dimensional system. In addition, the monoclinic $C2$ CDW-II phase may also be stable according to the phonon dispersion spectrum. Since these two phases have very similar energies in our density functional theory calculations, both these Ta-tetramerization distortions likely compete or coexist at low temperatures. The semimetal-to-insulator transition is induced by a Fermi-surface-driven instability that supports the Peierls scenario, which affects the Weyl physics developed above ${T}_{\mathrm{CDW}}$. Furthermore, the spin-orbit coupling generates Rashba-like band splittings in the insulating charge density wave phases.