title: Electronic cooling via interlayer Coulomb coupling in multilayer epitaxial graphene.
abstract: In van der Waals bonded or rotationally disordered multilayer stacks of two-dimensional (2D) materials, the electronic states remain tightly confined within individual 2D layers. As a result, electron-phonon interactions occur primarily within layers and interlayer electrical conductivities are low. In addition, strong covalent in-plane intralayer bonding combined with weak van der Waals interlayer bonding results in weak phonon-mediated thermal coupling between the layers. We demonstrate here, however, that Coulomb interactions between electrons in different layers of multilayer epitaxial graphene provide an important mechanism for interlayer thermal transport, even though all electronic states are strongly confined within individual 2D layers. This effect is manifested in the relaxation dynamics of hot carriers in ultrafast time-resolved terahertz spectroscopy. We develop a theory of interlayer Coulomb coupling containing no free parameters that accounts for the experimentally observed trends in hot-carrier dynamics as temperature and the number of layers is varied.
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA.|Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Momchil T
authors.initials: MT
authors.lastname: Mihnev
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: John R
authors.initials: JR
authors.lastname: Tolsma
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA.|Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Divin
authors.affiliation: Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109, USA.|International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China.
authors.forename: Dong
authors.initials: D
authors.lastname: Sun
authors.affiliation: School of Physics, Institute for Research in Fundamental Sciences (IPM), Tehran 19395-5531, Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Asgari
authors.affiliation: NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, Pisa I-56126, Italy.|Istituto Italiano di Tecnologia, Graphene Labs, Via Morego 30, Genova I-16163, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Polini
authors.affiliation: School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.|Institut Neel, CNRS UJF-INP, Grenoble 38042, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Berger
authors.affiliation: School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.|King Abdulaziz University, Jeddah 22254, Saudi Arabia.
authors.forename: Walt A
authors.initials: WA
authors.lastname: de Heer
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.
authors.forename: Allan H
authors.initials: AH
authors.lastname: MacDonald
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA.|Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Theodore B
authors.initials: TB
authors.lastname: Norris