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Charge density wave phase, Mottness, and ferromagnetism in monolayer 1TNbSe2

Diego Pasquier and Oleg V. Yazyev
Phys. Rev. B 98, 045114 – Published 10 July 2018
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Abstract

The recently investigated 1T polymorph of monolayer NbSe2 revealed an insulating behavior suggesting a star-of-David phase with 13×13 periodicity associated with a Mott insulator, reminiscent of 1TTaS2. We examine this novel two-dimensional material from first principles. We find an instability towards the formation of an incommensurate charge density wave (CDW) and establish the star-of-David phase as the most stable commensurate CDW. The Mottness in the star-of-David phase is confirmed and studied at various levels of theory: the spin-polarized generalized gradient approximation (GGA) and its extension involving the on-site Coulomb repulsion (GGA+U), as well as the dynamical mean-field theory. Finally, we estimate Heisenberg exchange couplings in this material and find a weak nearest-neighbor ferromagnetic coupling, at odds with most Mott insulators. We point out the close resemblance between this star-of-David phase and flat-band ferromagnetism models.

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  • Received 29 March 2018
  • Revised 4 June 2018

DOI:https://doi.org/10.1103/PhysRevB.98.045114

©2018 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Diego Pasquier* and Oleg V. Yazyev

  • Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

  • *diego.pasquier@epfl.ch
  • oleg.yazyev@epfl.ch

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Issue

Vol. 98, Iss. 4 — 15 July 2018

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