Large-gap insulating dimer ground state in monolayer IrTe2

TL;DR

This study discovers a large-gap insulating dimer ground state in monolayer IrTe2, contrasting with its bulk form, through combined experimental and theoretical approaches, revealing new insights into 2D material properties.

Contribution

It demonstrates the emergence of a unique insulating 2 x 1 dimer ground state in monolayer IrTe2, highlighting the role of reduced dimensionality and interactions.

Findings

Monolayer IrTe2 exhibits a large band gap and insulating ground state.

Charge and phonon instabilities stabilize the dimerized phase.

Experimental and theoretical results agree on the charge-ordered ground state.

Abstract

Monolayers of two-dimensional van der Waals materials exhibit novel electronic phases distinct from their bulk due to the symmetry breaking and reduced screening in the absence of the interlayer coupling. In this work, we combine angle-resolved photoemission spectroscopy and scanning tunneling microscopy/spectroscopy to demonstrate the emergence of a unique insulating 2 x 1 dimer ground state in monolayer 1T-IrTe2 that has a large band gap in contrast to the metallic bilayer-to-bulk forms of this material. First-principles calculations reveal that phonon and charge instabilities as well as local bond formation collectively enhance and stabilize a charge-ordered ground state. Our findings provide important insights into the subtle balance of interactions having similar energy scales that occurs in the absence of strong interlayer coupling, which offers new opportunities to engineer the properties of 2D monolayers.