title: Orbital-specific tunability of many-body effects in bilayer graphene by gate bias and metal contact.
abstract: Graphene, a 2D crystal bonded by π and σ orbitals, possesses excellent electronic properties that are promising for next-generation optoelectronic device applications. For these a precise understanding of quasiparticle behaviour near the Dirac point (DP) is indispensable because the vanishing density of states (DOS) near the DP enhances many-body effects, such as excitonic effects and the Anderson orthogonality catastrophe (AOC) which occur through the interactions of many conduction electrons with holes. These effects renormalize band dispersion and DOS, and therefore affect device performance. For this reason, we have studied the impact of the excitonic effects and the AOC on graphene device performance by using X-ray absorption spectromicroscopy on an actual graphene transistor in operation. Our work shows that the excitonic effect and the AOC are tunable by gate bias or metal contacts, both of which alter the Fermi energy, and are orbital-specific.
authors.affiliation: Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aobaku-ku, Sendai, Miyagi 980-8577, Japan.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Fukidome
authors.affiliation: JASRI/SPring-8, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Kotsugi
authors.affiliation: Department of Materials Engineering, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Tokyo 113-8656, Japan.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Nagashio
authors.affiliation: Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aobaku-ku, Sendai, Miyagi 980-8577, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Sato
authors.affiliation: JASRI/SPring-8, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan.
authors.forename: Takuo
authors.initials: T
authors.lastname: Ohkochi
authors.affiliation: Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, 6-3 Aoba, Aoba-ku, Sendai, Miyagi 980-7578, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Itoh
authors.affiliation: Department of Materials Engineering, Graduate School of Engineering, University of Tokyo, 7-3-1 Hongo, Tokyo 113-8656, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Toriumi
authors.affiliation: Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aobaku-ku, Sendai, Miyagi 980-8577, Japan.
authors.forename: Maki
authors.initials: M
authors.lastname: Suemitsu
authors.affiliation: JASRI/SPring-8, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan.
authors.forename: Toyohiko
authors.initials: T
authors.lastname: Kinoshita