Title: Layer-dependent topological phase in a two-dimensional quasicrystal and approximant

Abstract

The electronic and topological properties of materials are derived from the interplay between crystalline symmetry and dimensionality. Simultaneously introducing “forbidden” symmetries via quasiperiodic ordering with low dimensionality into a material system promises the emergence of new physical phenomena. Here, we isolate a two-dimensional (2D) chalcogenide quasicrystal and approximant, and investigate their electronic and topological properties. The 2D layers of the materials with a composition close to Ta _1.6 Te, derived from a layered transition metal dichalcogenide, are isolated with standard exfoliation techniques, and investigated with electron diffraction and atomic resolution scanning transmission electron microscopy. Density functional theory calculations and symmetry analysis of the large unit cell crystalline approximant of the quasicrystal, Ta ₂₁ Te ₁₃ , reveal the presence of symmetry-protected nodal crossings in the quasicrystalline and approximant phases, whose presence is tunable by layer number. Our study provides a platform for the exploration of physics in quasicrystalline, low-dimensional materials and the interconnected nature of topology, dimensionality, and symmetry in electronic systems.

Authors:

Cain, Jeffrey D.; Azizi, Amin ;

• Search DOE PAGES for author "Azizi, Amin"
• Search DOE PAGES for ORCID "0000-0001-9955-7228"

Conrad, Matthias; Griffin, Sinéad M.; Zettl, Alex

Publication Date:

Mon Oct 05 00:00:00 EDT 2020

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division

OSTI Identifier:

1670472

Alternate Identifier(s):

OSTI ID: 1695764

Grant/Contract Number:  

AC02-05-CH11231; AC02-05CH11231

Resource Type:

Published Article

Journal Name:

Proceedings of the National Academy of Sciences of the United States of America

Additional Journal Information:

Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Volume: 117 Journal Issue: 42; Journal ID: ISSN 0027-8424

Publisher:

National Academy of Sciences

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; two-dimensional materials; quasicrystals; approximant; scanning transmission electron microscopy; topological materials