Doping-tunable charge ordering in semiconducting single-layer Cr₂Se₃.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Surface Science

Background:

• Charge density waves (CDWs) are crucial for understanding electron interactions and quantum phase transitions.
• Carrier density significantly impacts CDW ground states, typically modified by doping.
• Atomic-scale visualization of CDW in doped systems, especially without foreign ions, is challenging.

Purpose of the Study:

• To visualize and understand doping-tunable granular charge ordering in semiconducting single-layer Cr2Se3.
• To investigate the atomic-scale effects of doping on CDW behavior in a group VIB transition metal chalcogenide.

Main Methods:

• Scanning tunneling microscopy (STM) for real-space atomic-scale observation.
• Investigation of lattice distortion, bandgap modulation at the Fermi level (EF), and STM contrast inversion.
• Controlled doping (hole and electron) to modulate charge ordering.

Main Results:

• Real-space observation of granular charge ordering in Cr2Se3.
• Evidence of charge ordering through lattice distortion, bandgap modulation, and STM contrast inversion.
• Doping-dependent modulation: hole doping suppresses CDW, while electron doping induces a periodic 3√3 × 3√3 CDW phase.

Conclusions:

• Semiconducting single-layer Cr2Se3 exhibits doping-tunable granular charge ordering.
• This work provides atomic-scale insights into charge doping and ordering interactions in two-dimensional materials.
• Advances understanding of CDW phenomena in group VIB transition metal chalcogenides.