Probing embedded topological modes in bulk-like GeTe-Sb₂Te₃ heterostructures

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Topological insulators exhibit unique metallic surface states due to band topology.
• Research has focused on surface states, but solid-solid interface states are less understood.
• Embedded topological states (ETSs) at heterostructure interfaces present novel research avenues.

Purpose of the Study:

• Investigate embedded topological states (ETSs) in GeTe/Sb[Formula: see text]Te[Formula: see text] heterostructures.
• Analyze the dependence of ETSs on interface properties and their confinement.
• Explore the robustness and delocalization characteristics of interfacial topological modes.

Main Methods:

• Combined experimental and theoretical approaches.
• X-ray photoemission spectroscopy (XPS) to evaluate band offset.
• Atom probe tomography (APT) for elemental composition analysis.
• First-principles calculations for band offset and band structure parametrization.
• Four-band continuum model for band structure analysis.

Main Results:

• Interfacial topological modes are delocalized over multiple lattice spacings under realistic conditions.
• First-principles calculations show ETSs possess relative robustness against disorder.
• Characterized band offset and elemental composition of GeTe-Sb[Formula: see text]Te[Formula: see text] heterostructures.

Conclusions:

• ETSs in normal-topological insulator heterostructures exhibit delocalized and robust characteristics.
• Findings provide insights into manipulating topological modes in solid-solid interfaces.
• The study supports and explains recent experimental observations of coupled ETSs over thick layers.