Edge States at Nematic Domain Walls in FeSe Films

Area of Science:

• Condensed matter physics
• Materials science
• Quantum phenomena

Background:

• The Quantum Spin Hall (QSH) effect is a quantum mechanical phenomenon observed in specific materials.
• It is characterized by the presence of conducting edge states while the bulk remains insulating.
• Understanding and realizing the QSH effect is crucial for developing novel electronic devices and exploring topological quantum computation.

Purpose of the Study:

• To investigate the potential of FeSe films in exhibiting the Quantum Spin Hall (QSH) effect.
• To explore the role of nematic domain boundaries in achieving topological band inversion and edge states.
• To provide a new material platform for realizing topological superconductivity.

Main Methods:

• Fabrication of FeSe films with atomically sharp nematic domain boundaries using molecular beam epitaxy (MBE).
• Characterization of the films using scanning tunneling microscopy (STM) to observe edge states.
• Theoretical validation using density functional theory (DFT) calculations to confirm the topological origin of observed phenomena.

Main Results:

• Atomically sharp nematic domain boundaries were successfully created in FeSe films.
• Tensile strains, nematicity suppression, and topological band inversion were simultaneously achieved at these boundaries.
• Edge states at the Fermi level were observed as distinct strips near the domain boundaries, with a bound state at their endpoints.
• DFT calculations supported the topological nature of the observed edge states.

Conclusions:

• FeSe films with engineered domain boundaries serve as a promising candidate for realizing the Quantum Spin Hall (QSH) effect.
• The study demonstrates a novel approach to achieving QSH states and topological superconductivity within a single-component material.
• This work opens new avenues for the design and synthesis of materials with exotic topological properties.