title: Mass-related inversion symmetry breaking and phonon self-energy renormalization in isotopically labeled AB-stacked bilayer graphene.
abstract: A mass-related symmetry breaking in isotopically labeled bilayer graphene (2LG) was investigated during in-situ electrochemical charging of AB stacked (AB-2LG) and turbostratic (t-2LG) layers. The overlap of the two approaches, isotopic labeling and electronic doping, is powerful tool and allows to tailor, independently and distinctly, the thermal-related and transport-related phenomena in materials, since one can impose different symmetries for electrons and phonons in these systems. Variations in the system's phonon self-energy renormalizations due to the charge distribution and doping changes could be analyzed separately for each individual layer. Symmetry arguments together with first-order Raman spectra show that the single layer graphene (1LG), which is directly contacted to the electrode, has a higher concentration of charge carriers than the second graphene layer, which is not contacted by the electrode. These different charge distributions are reflected and demonstrated by different phonon self-energy renormalizations of the G modes for AB-2LG and for t-2LG.
authors.affiliation: Department of Electrical Engineering and Computer Science, MIT, Cambridge, Massachusetts 02139, USA. ptaraujo@mit.edu
authors.forename: Paulo T
authors.initials: PT
authors.lastname: Araujo
authors.forename: Otakar
authors.initials: O
authors.lastname: Frank
authors.forename: Daniela L
authors.initials: DL
authors.lastname: Mafra
authors.forename: Wenjing
authors.initials: W
authors.lastname: Fang
authors.forename: Jing
authors.initials: J
authors.lastname: Kong
authors.forename: Mildred S
authors.initials: MS
authors.lastname: Dresselhaus
authors.forename: Martin
authors.initials: M
authors.lastname: Kalbac