• 文献标题:   Ultrafast Dynamics of Massive Dirac Fermions in Bilayer Graphene
  • 文献类型:   Article
  • 作  者:   ULSTRUP S, JOHANNSEN JC, CILENTO F, MIWA JA, CREPALDI A, ZACCHIGNA M, CACHO C, CHAPMAN R, SPRINGATE E, MAMMADOV S, FROMM F, RAIDEL C, SEYLLER T, PARMIGIANI F, GRIONI M, KING PDC, HOFMANN P
  • 作者关键词:  
  • 出版物名称:   PHYSICAL REVIEW LETTERS
  • ISSN:   0031-9007 EI 1079-7114
  • 通讯作者地址:   Aarhus Univ
  • 被引频次:   62
  • DOI:   10.1103/PhysRevLett.112.257401
  • 出版年:   2014

▎ 摘  要

Bilayer graphene is a highly promising material for electronic and optoelectronic applications since it is supporting massive Dirac fermions with a tunable band gap. However, no consistent picture of the gap's effect on the optical and transport behavior has emerged so far, and it has been proposed that the insulating nature of the gap could be compromised by unavoidable structural defects, by topological in-gap states, or that the electronic structure could be altogether changed by many-body effects. Here, we directly follow the excited carriers in bilayer graphene on a femtosecond time scale, using ultrafast time- and angle-resolved photoemission. We find a behavior consistent with a single-particle band gap. Compared to monolayer graphene, the existence of this band gap leads to an increased carrier lifetime in the minimum of the lowest conduction band. This is in sharp contrast to the second substate of the conduction band, in which the excited electrons decay through fast, phonon-assisted interband transitions.