09:30 〜 09:45
[2Fa05] Study of layer-dependent dynamics of Dirac Fermions in quasi-crystalline bilayer graphene by concerting usages of positron diffraction and time-resolved photoemission spectroscopy
Dynamical behavior of carriers in graphene has attracted academic interests to investigate temporal evolutions of the massless Dirac Fermions and also technical needs to develop the next-generation optoelectronic devices. The comprehensive understanding has been conducted by direct observations of the electronic states by time- and angle-resolved photoemission spectroscopy (TARPES). TARPES measurements on the epitaxial quasi-crystalline bilayer graphene observed the transient voltage between the two layers that were not expected theoretically. The experimental reasoning has required contributions from the substrate or the interface but the detailed scenario has remained unknown. In the present research, we performed TARPES measurements on various systems of single and bilayer graphene on the Si-face SiC substrates to extensively study the carrier dynamics. The quantitative discussion was made with the structural parameters, interlayer distance, determined by positron diffraction (PD) experiments. The concerting usages of TARPES and PD quantitatively revealed the transport mechanism that was induced by the optical pumping.