Theory of competing excitonic orders in insulating WTe2 monolayers

Yves H. Kwan, T. Devakul, S. L. Sondhi, S. A. Parameswaran

Research output: Contribution to journalArticlepeer-review

Abstract

We develop a theory of the excitonic phase recently proposed as the zero-field insulating state observed near charge neutrality in monolayer WTe2. Using a Hartree-Fock approximation, we numerically identify two distinct gapped excitonic phases: a spin density wave state for weak nonzero interaction strength and spin spiral order at stronger interactions, separated by a narrow window of a nonexcitonic quantum spin Hall insulator. We introduce a simplified model capturing key features of the WTe2 band structure, in which these phases appear as distinct valley ferromagnetic orders. We link the competition between the excitonic phases to the orbital structure of electronic wave functions at the Fermi surface and hence its proximity to the underlying gapped Dirac point in WTe2. We briefly discuss collective modes of the two excitonic states, and comment on implications for experiments.

Original languageEnglish (US)
Article number125133
JournalPhysical Review B
Volume104
Issue number12
DOIs
StatePublished - Sep 15 2021
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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