Unified microscopic description of the origin and interplay between CDW and superconducting order in TiSe2

ORAL

Abstract

We theoretically address the striking interplay between charge density wave (CDW) order and superconductivity (SC) in 1T-TiSe2, whose microscopic details are under active scrutiny. Starting with undoped TiSe2, the commensurate CDW instability is captured microscopically by the mechanism of excitonic condensation involving interactions among the overlapping electron and hole pockets characteristic of this material. Fixing the only parameter in the theory to the undoped state, the predicted reduction of Tcdw with doping follows the experimental curve without further fitting. A Ginzburg-Landau theory further shows that the transition to the incommensurate CDW phase as a function of doping takes place via an intervening near-commensurate regime, characterized by the proliferation of discommensurations. As these are simply fluctuations of the CDW, we investigated the spectrum of fluctuations predicted by the microscopic model and found they induce s-wave pairing among the quasiparticles of the excitonic condensate. The predicted SC transition temperature as a function of doping is dome-shapped, precisely as in the experiments, and our estimated Tsc is in satisfactory agreement. We are thus able to capture the full CDW and SC phase diagram within a single microscopic picture.

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Presenters

  • Vitor Pereira

    Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore 117546, National University of Singapore, Department of Physics, National University of Singapore, Centre for Advanced 2D Materials, National University of Singapore

Authors

  • Vitor Pereira

    Centre for Advanced 2D Materials, National University of Singapore, 6 Science Drive 2, Singapore 117546, National University of Singapore, Department of Physics, National University of Singapore, Centre for Advanced 2D Materials, National University of Singapore

  • Chuan Chen

    Department of Physics, National University of Singapore, National University of Singapore

  • Lei Su

    Department of Physics, University of Chicago

  • Bahadur Singh

    SZU-NUS Collaborative Center and International Collaborative Laboratory of 2D Materials for Optoelectronic Science & Technology, Engineering Technology Research Center for 2D, Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA /SZU-NUS Collaborative Center and International Collaborative Laboratory of 2D Materials for, Department of Physics, National University of Singapore, SZU-NUS Collaborative Center and International Collaborative Laboratory of 2D Materials for Optoelectronic Science \& Technology, Engineering Technology Research Center for 2, Department of Physics, Northeastern University, Shenzhen University, Shenzhen, China, College of Optoelectronic Engineering, Shenzhen University

  • Antonio Helio Castro Neto

    National University of Singapore, Department of Physics, National University of Singapore, Centre for Advanced 2D Materials, National University of Singapore

  • Hsin Lin

    Academia Sinica, Institute of Physics, Academia Sinica, Physics, Academia Sinica, Taipei 11529, Taiwan, Institute of Physics, Academia Sinica, Taipei 11529, Taiwan, Physics, Academia Sinica, Department of Physics, National University of Singapore, National University of Singapore, Academia Sinica, Taipei, Taiwan