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Mechanism for electronic and structural phase transitions in Ta<sub>2</sub>NiSe<sub>5</sub>

ORAL

Abstract

Ta2NiSe5 undergoes a second-order phase transition from a high-temperature orthorhombic phase to a low-temperature monoclinic phase at around 330K, accompanied by a metal-to-insulator transition. It has been intensively debated whether the transition is induced by excitonic effects or structural and lattice distortions. We use density functional theory (DFT), which in principle does not include any excitonic effects, to explore a non-excitonic mechanism to explain the electronic and structural phase transitions in Ta2NiSe5. The low-temperature monoclinic crystal structure can be obtained directly from the structure relaxation, and the corresponding electronic structure shows an M-shaped valence band top. We further study this system under S (sulfur) doping (replacing Se) and potassium dosing (introducing electron carriers). The theoretical results are in good agreement with recent high-energy X-ray diffraction (XRD) and angle-resolved photoemission spectroscopy (ARPES) data [1, 2]. Our first-principles study based on DFT suggests that a non-excitonic mechanism can explain the phase transitions in Ta2NiSe5, without invoking any excitonic effects.

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Publication: [1] C. Chen, X. Chen, W. Tang, Z. Li, S. Wang, S. Ding, C. Jozwiak, A. Bostwick, E. Rotenberg, M. Hashimoto, D. Lu, J. Ruff, S. G. Louie, R. Birgeneau, Y. Chen, Y. Wang, Y. He, Lattice fluctuation induced pseudogap in quasi-one-dimensional Ta2NiSe5 (submitted).<br>[2] C. Chen, W. Tang, X. Chen, Z. Kang, K. Scott, S. Wang, Z. Li, J. Ruff, M. Hashimoto, D. Lu, C. Jozwiak, A. Bostwick, E. Rotenberg, E. da Silva Neto, R. Birgeneau, Y. Chen, S. G. Louie, Y. Wang, Y. He, in preparation.

Presenters

  • Weichen Tang

    University of California, Berkeley

Authors

  • Weichen Tang

    University of California, Berkeley

  • Zhenglu Li

    Lawrence Berkeley National Laboratory, University of California at Berkeley, and Lawrence Berkeley National Laboratory

  • Steven G Louie

    University of California at Berkeley, University of California, Berkeley, University Of California, Berkeley, University of California at Berkeley and Lawrence Berkeley National Lab, University of California at Berkeley; Lawrence Berkeley National Lab, UC Berkeley, University of California at Berkeley, and Lawrence Berkeley National Laboratory, UC berkeley, Lawrence Berkeley National Laboratory, Physics Department, UC Berkeley and Lawrence Berkeley National Lab, Department of Physics, University of California at Berkeley and Materials Sciences Division, Lawrence Berkeley National Laboratory, LBNL & UC Berkeley