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

Area of Science:

• Condensed Matter Physics
• Materials Science
• Crystallography

Background:

• Electronic and topological properties arise from the interplay of crystalline symmetry and dimensionality.
• Introducing "forbidden" symmetries via quasiperiodic ordering in low-dimensional systems can lead to novel physical phenomena.

Purpose of the Study:

• To investigate the electronic and topological properties of two-dimensional (2D) chalcogenide quasicrystals and their crystalline approximants.
• To explore the emergence of new physical phenomena in low-dimensional materials with quasiperiodic ordering.

Main Methods:

• Isolation of 2D chalcogenide layers (Ta _1.6Te) using standard exfoliation techniques.
• Characterization via electron diffraction and atomic resolution scanning transmission electron microscopy.
• Electronic structure calculations using density functional theory (DFT) and symmetry analysis on a large unit cell crystalline approximant (Ta ₂₁Te ₁₃).

Main Results:

• Identification of symmetry-protected nodal crossings in the electronic band structure of the quasicrystalline and approximant phases.
• Demonstration that the presence of these nodal crossings is tunable by the layer number.
• Confirmation of the interplay between symmetry, dimensionality, and topology in these novel materials.

Conclusions:

• The studied 2D chalcogenide quasicrystals and approximants serve as a platform for exploring unique physics.
• This work highlights the interconnectedness of topology, dimensionality, and symmetry in electronic systems.
• The findings pave the way for designing materials with tailored electronic and topological properties.