Nanoscale Conducting and Insulating Domains on YbB_{6}

Area of Science:

• Condensed Matter Physics
• Materials Science
• Surface Science

Background:

• Ytterbium hexaboride (YbB_{6}) is theoretically a topological insulator.
• Experimental observations show conducting surface states, but their origin is unclear.
• Lack of natural cleavage and surface polarity hinder YbB_{6} research.

Purpose of the Study:

• To investigate the surface structure and electronic properties of cleaved YbB_{6}.
• To clarify the nature of conducting surface states in YbB_{6}.
• To assess the potential of YbB_{6} for spintronic applications.

Main Methods:

• Scanning tunneling microscopy (STM) was used to image cleaved YbB_{6} surfaces.
• Spectroscopic measurements were performed to analyze electronic properties.
• Atomic structures of different surface terminations were characterized.

Main Results:

• Cleaved YbB_{6} surfaces exhibit multiple coexisting terminations with distinct atomic structures.
• Band bending between terminations creates both conducting and fully gapped (insulating) domains.
• Conducting domains show spectral peaks consistent with Van Hove singularities from Rashba spin-split quantum well states.

Conclusions:

• The presence of insulating domains excludes YbB_{6} as a strong topological insulator.
• Spin-polarized conducting domains indicate potential applications in spintronics.
• Understanding surface terminations is crucial for YbB_{6} research.