Dirac Velocity modification on Epitaxial Graphene
Jhih-Wei Chen1*, Camilla Coletti4, Hao-Chun Huang1, Hung-Wei Shiu2, Lo-Yeuh Chang3, Cheng-Maw Cheng2, Min-Fa Lin1, Stefan Heun4, Chia-Hao Chen2, Yi-Chun Chen1, Chung-Lin Wu1
1Department of Physics, National Cheng Kung University, Tainan, Taiwan
2National Synchrotron Radiation Research Center, HsinChu, Taiwan
3Department of Physics, National Tsing Hua University, HsinChu, Taiwan
4National Enterprise for nanoScience and nanotechnology, Pisa, Italy
* presenting author:Jhih-Wei Chen, email:l28991013@mail.ncku.edu.tw
Graphene is a unique low-dimensional system with fascinating electrical properties including linear electron energy dispersion and high room-temperature mobility, which has been considered a prospective candidate for post silicon electronics. To fully characterize the electron-electron interaction in the epitaxial graphene system, the angle-resolved photoemission spectroscopy (ARPES) was used here to in-situ illustrate the electronic structure modulation of graphene covered by transition metal. The significant change of graphene Dirac velocity, which can be monitored by ARPES, was found for the first time. The Dirac velocity change in graphene can be attributed to the excess charge carriers screening by transition metal, which causes the renormalization of the Dirac cone across the measurable energy interval. The DFT theoretical calculation revealed the excess carriers uniformly distributed around the graphene surface, which result from the in-plane delocalized d-orbital charges of transition metal.

Keywords: Graphene, Dirac velocity, transition metal