Abundance of second order topology in C3 symmetric two-dimensional insulators

Joachim Sødequist, Urko Petralanda, Thomas Olsen*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

12 Downloads (Pure)

Abstract

We have screened 71 two-dimensional (2D) materials with C3 symmetry for non-trivial second order topological order and find that 28 compounds exhibit an obstructed atomic limit (OAL). In the case of C3 symmetry, the second order topology can be calculated from bulk symmetry indicator invariants, which predict the value of fractional corner charges in symmetry conserving nanoflakes. The procedure is exemplified by MoS2 in the H-phase, which constitutes a generic example of a 2D OAL material and the predicted fractional corner charges is verified by direct calculations of nanoflakes with armchair edges. We also determine the bulk topological polarization, which always lead to gapless states at zigzag edges and thus deteriorates the concept of fractional corner charges in nanoflakes with zigzag edges that are typically more stable that armchair flakes. We then consider the case of TiCl2, which has vanishing polarization as well as an OAL and we verify that the edge states of nanoflakes with zigzag edges may indeed by passivated such that the edges remain insulating and the corner charges are well defined. For the 28 OAL materials we find that 16 have vanishing polarization and these materials thus constitute a promising starting point for experimental verification of second order topology in a 2D material.
Original languageEnglish
Article number015009
Journal2D materials
Volume10
Number of pages7
ISSN2053-1583
DOIs
Publication statusPublished - 2023

Keywords

  • Higher order topology
  • Density functional theory
  • 2D materials
  • Topological insulators

Fingerprint

Dive into the research topics of 'Abundance of second order topology in C3 symmetric two-dimensional insulators'. Together they form a unique fingerprint.

Cite this