Journal
PHYSICAL REVIEW B
Volume 88, Issue 3, Pages -Publisher
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.88.035430
Keywords
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Funding
- Italian Ministry of Education, University, and Research (MIUR) through the program FIRB - Futuro in Ricerca [RBFR10M5BT]
- ERC [291198]
- EU
- Royal Society Wolfson Research Merit Award
- EPSRC [EP/K017144/1, EP/K01711X/1, EP/GO30480/1, EP/G042357/1]
- Cambridge Nokia Research Centre
- Engineering and Physical Sciences Research Council [EP/G042357/1, EP/G030480/1, EP/K01711X/1, EP/K017144/1] Funding Source: researchfish
- European Research Council (ERC) [291198] Funding Source: European Research Council (ERC)
- EPSRC [EP/K01711X/1, EP/K017144/1, EP/G042357/1, EP/G030480/1] Funding Source: UKRI
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We present a combined analytical and numerical study of the early stages (sub-100-fs) of the nonequilibrium dynamics of photoexcited electrons in graphene. We employ the semiclassical Boltzmann equation with a collision integral that includes contributions from electron-electron (e-e) and electron-optical phonon interactions. Taking advantage of circular symmetry and employing the massless Dirac fermion (MDF) Hamiltonian, we are able to perform an essentially analytical study of the e-e contribution to the collision integral. This allows us to take particular care of subtle collinear scattering processes-processes in which incoming and outgoing momenta of the scattering particles lie on the same line-including carrier multiplication (CM) and Auger recombination (AR). These processes have a vanishing phase space for two-dimensional MDF bare bands. However, we argue that electron-lifetime effects, seen in experiments based on angle-resolved photoemission spectroscopy, provide a natural pathway to regularize this pathology, yielding a finite contribution due to CM and AR to the Coulomb collision integral. Finally, we discuss in detail the role of physics beyond the Fermi golden rule by including screening in the matrix element of the Coulomb interaction at the level of the random phase approximation (RPA), focusing in particular on the consequences of various approximations including static RPA screening, which maximizes the impact of CM and AR processes, and dynamical RPA screening, which completely suppresses them.
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