Carrier Dynamics in Graphene: Ultrafast Many‐Particle Phenomena

Abstract

Graphene is an ideal material to study fundamental Coulomb-and phonon-induced carrier scattering processes. Its remarkable gapless and linear band structure opens up new carrier relaxation channels. In particular, Auger scattering bridging the valence and the conduction band changes the number of charge carriers and gives rise to a significant carrier multiplicationan ultrafast many-particle phenomenon that is promising for the design of highly efficient photodetectors. Furthermore, the vanishing density of states at the Dirac point combined with ultrafast phonon-induced intraband scattering results in an accumulation of carriers and a population inversion suggesting the design of graphene-based terahertz lasers. Here, we review our work on the ultrafast carrier dynamics in graphene and Landau-quantized graphene is presented providing a microscopic view on the appearance of carrier multiplication and population inversion.

Hyperbolic Phonon Polariton Electroluminescence as an Electronic Cooling Pathway

“…In contrast to this well‐known configuration, graphene has no bandgap, however, the threshold energy is now the RS band energy μ c − μ v ≲ ℏΩ II . For unbiased graphene, out‐of‐equilibrium electronic distribution can be transiently created by optical pumping and have been observed to relax on sub‐ps timescales by optical pump–probe techniques . In the next section, we show that electrical pumping of charges occurs similarly in high mobility graphene under large bias and leads to a favorable situation for HPhP electroluminescence cooling.…”

Carrier-envelope phase effects in graphene

“…Second, for longer pulses with duration of 100 fs or more, the effect of electronelectron scattering increases. Indeed, as mentioned earlier, the typical scattering time scale is a few tens of femtoseconds [38]. The main effect of scattering is to steer the system towards equilibrium with a Fermi-Dirac-like isotropic EMD.…”

“…This is because, as detailed in Refs. [38,39] the largest reported thermalization times in graphene are a few hundreds of femtoseconds, which is shorter than the duration of a few-cycle THz pulse. Consequently, the observability of anisotropic momentum-space distributions with THz pump beams implies experimental precautions to increase the thermalization time in graphene to the picosecond range [16,40].…”

Silicon/2D-material photodetectors: from near-infrared to mid-infrared

“…As illustrated in Fig. 1g, the thermal relaxation process in 2DMs is briefly described by a well-known two-temperature system [47][48][49] . After the photo-excited e-h pairs generate under illumination, the electron heating occurs by the carrier-carrier scattering, leading to the increment of the electron temperature T e .…”