Charge Density Wave Phase Transition on the Surface of Electrostatically Doped Multilayer Graphene

TL;DR

This study demonstrates that charge density wave (CDW) phase transitions occur on the surface of electrostatically doped multilayer graphene near van Hove singularities, evidenced by electrical and optical measurements including resistance changes and Raman peak splitting.

Contribution

It provides experimental evidence of CDW phase transitions in multilayer graphene induced by electrostatic doping near van Hove singularities, linking electronic and lattice structural changes.

Findings

CDW transition occurs at T_m = 100K.

Resistance changes sharply at the transition.

Raman G peak splits indicating lattice reconstruction.

Abstract

We demonstrate that charge density wave (CDW) phase transition occurs on the surface of electronically doped multilayer graphene when the Fermi level approaches the M points (also known as van Hove singularities where the density of states diverge) in the Brillouin zone of graphene band structure. The occurrence of such CDW phase transitions are supported by both the electrical transport measurement and optical measurements in electrostatically doped multilayer graphene. The CDW transition is accompanied with the sudden change of graphene channel resistance at T$_m$= 100K, as well as the splitting of Raman G peak (1580 cm$^{-1}$). The splitting of Raman G peak indicats the lifting of in-plane optical phonon branch degeneracy and the non-degenerate phonon branches are correlated to the lattice reconstructions of graphene -- the CDW phase transition.