Real Space Imaging of Topological Edge States in InAs/GaSb and InAs/InGa_1-Sb Quantum Wells

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Two-dimensional topological insulators (2D-TIs) are materials with unique electronic properties, including conducting edge states protected by time-reversal symmetry.
• InAs/GaSb and related quantum well systems are promising platforms for realizing 2D-TIs due to their tunable band structures.

Purpose of the Study:

• To investigate the presence and characteristics of edge states on the surfaces of InAs/GaSb and InAs/InGaSb quantum wells.
• To confirm the experimental findings with theoretical electronic structure calculations.

Main Methods:

• Utilizing scanning tunneling microscopy (STM) to measure differential tunneling conductance (dI/dV) profiles.
• Performing k·p-based electronic structure calculations to model the material's behavior.

Main Results:

• STM measurements clearly demonstrated structure-dependent differential tunneling conductance profiles on both (110)-cleaved and (001)-growth surfaces.
• The experimental results provided direct evidence for the formation of edge states on the 2D-TI surfaces.
• k·p calculations confirmed the existence of these edge states and showed they extended approximately 10 nm from the cleaved surfaces.

Conclusions:

• The study successfully identified and characterized edge states in InAs/GaSb-based 2D-TI systems.
• The findings validate the potential of these quantum wells as platforms for exploring topological phenomena.
• The extended range of edge states has implications for device design and fabrication in topological electronics.