Effect of microscopic scattering on the nonlinear transmission of terahertz fields through monolayer graphene

Abstract

We consider the nonlinear terahertz response of n-doped monolayer graphene at room temperature using a microscopic theory of carrier dynamics. Our tight-binding model treats the carrier-field interaction in the length gauge, includes phonon as well as short-range neutral-impurity scattering, and fully accounts for the intrinsic nonlinear response of graphene near the Dirac point. Treating each interaction microscopically allows us to separate contributions from current clipping, phonon creation, and elastic impurity scattering. Although neutral impurity scattering and phonon scattering are both highly energy-dependent, we find that they impact conduction-band electron dynamics very differently, and that together they can help explain experimental results concerning field-dependent terahertz transmission through graphene. arXiv:1811.02730v1 [cond-mat.mes-hall]

Pump-induced terahertz anisotropy in bilayer graphene

“…For a quantitative comparison with the experiment, we have performed simulations using a density matrix formalism in k-space. The dynamic equation for the reduced density matrix elements for carriers in the conduction band is given by the Boltzmann equation, 34,35…”

“…To obtain better quantitative agreement, one should include microscopic scattering due to neutral and charged impurities, phonons and electron-electron interactions. We have included the effects of neutral impurity and optical phonon scattering on the nonlinear THz transmission of monolayer graphene in previous work 35 and found that this generally leads to a stronger nonlinearity relative to simulations with a constant scattering time. We plan to include these effects and others on the differential transmission of bilayer graphene in future work.…”

The impact of nitrogen doping on the linear and nonlinear terahertz response of graphene

“…Both chemical vapour deposition [7] and epitaxial graphene growth [8] techniques have matured since graphene's emergence in 2004 [4]. Although there are many theoretical papers on the linear and nonlinear optical and terahertz response of pristine graphene, [9][10][11][12] to our knowledge, a comprehensive theoretical examination of carrier dynamics in non-pristine graphene [13][14][15] has not yet been carried out. In this work we examine the impact of nitrogen doping on the linear and nonlinear response of graphene to terahertz (THz) radiation.…”

“…Some include impurities phenomenologically via scattering times but retain the linear energy dispersion curves of pristine graphene. [11,18,34,35]. Such approaches neglect the effect of defects on the band structure, such as the opening of a band gap.…”

“…On the other hand ab initio studies have mainly focused on the band structure [36], material characteristics at optical frequencies [37][38][39], or carrier dynamics for low-intensity incident fields [40]. Previous work in our group focused on the linear and nonlinear response of monolayer and bilayer graphene to terahertz radiation, and the interplay between carrier dynamics, phonon scattering and neutral impurity scattering using a microscopic scattering model, but neglected impurityinduced changes in the electronic structure [9][10][11]22]. In the present work we combine a density functional tight binding method along with a density matrix treatment of carrier dynamics and phenomenological scattering to study the effects of nitrogen doping on the linear and nonlinear THz response of graphene.…”