Suppression of Intervalley Coupling in Graphene via Potassium Doping

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• Impurities in graphene create quantum interference patterns forming a (√3 × √3)R30° superlattice.
• This superlattice facilitates intervalley scattering, leading to a folded Dirac cone at the Brillouin zone center by coupling non-equivalent valleys.

Purpose of the Study:

• To investigate the effect of potassium doping on the folded Dirac cone in graphene superlattices.
• To understand how doping influences intervalley scattering and chiral symmetry.

Main Methods:

• Angle-resolved photoemission spectroscopy (ARPES) was used to observe the electronic band structure.
• Mono- and bilayer graphene samples were doped with potassium.

Main Results:

• Potassium doping was observed to suppress the folded Dirac cone in graphene.
• Intervalley coupling persisted at low doping levels but was destroyed at high doping.
• The Dirac band underwent renormalization due to potassium doping, contributing to the suppression.

Conclusions:

• Potassium doping effectively suppresses intervalley scattering and the folded Dirac cone in graphene superlattices.
• The findings suggest potential applications in developing novel chiraltronic devices.