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

L. G. Helt and M. M. Dignam

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.99.115413

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.

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Abstract-The effect of microscopic scattering on the nonlinear transmission of terahertz fields through monolayer graphene

L. G. Helt, M. M. Dignam

https://arxiv.org/abs/1811.02730

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.

Abstract-Effects of environmental conditions on the ultrafast carrier dynamics in graphene revealed by terahertz spectroscopy

H. A. Hafez, X. Chai, Y. Sekine, M. Takamura, K. Oguri, I. Al-Naib, M. M. Dignam, H. Hibino, and T. Ozaki

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.95.165428

A thorough understanding of the stability of graphene under ambient environmental conditions is essential for future graphene-based applications. In this paper, we study the effects of ambient temperature on the properties of monolayer graphene using terahertz time-domain spectroscopy as well as time-resolved terahertz spectroscopy enabled by an optical-pump/terahertz-probe technique. The observations show that graphene is extremely sensitive to the ambient environmental conditions and behaves differently depending on the sample preparation technique and the initial Fermi level. The analysis of the spectroscopic data is supported by van der Pauw and Hall effect measurements of the carrier mobility and carrier density at temperatures comparable to those tested in our THz spectroscopic experiments.

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Abstract-Nonlinear transmission of an intense terahertz field through monolayer graphene

H. A. Hafez¹, I. Al-Naib², K. Oguri³, Y. Sekine³, M. M. Dignam², A. Ibrahim¹,D. G. Cooke⁴, S. Tanaka⁵, F. Komori⁶, H. Hibino³ and T. Ozaki^1,a)

http://scitation.aip.org/content/aip/journal/adva/4/11/10.1063/1.4902096
1 INRS-EMT, Advanced Laser Light Source, INRS, Varennes, Québec J3X 1S2, Canada
2 Department of Physics, Engineering Physics and Astronomy, Queen’s University, Kingston, Ontario K7L 3N6, Canada
3 NTT Basic Research Laboratories, NTT Corporation, Atsugi, Kanagawa 243-0198, Japan
4 Department of Physics, McGill University, Montréal, Québec, H3A 2T8, Canada
5 Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka 819-0395, Japan
6 Institute for Solid State Physics, University of Tokyo, Chiba, 277-8581, Japan
a) Author to whom correspondence should be addressed. Electronic mail: ozaki@emt.inrs.ca
AIP Advances 4, 117118 (2014); http://dx.doi.org/10.1063/1.4902096

We report nonlinear terahertz (THz) effects in monolayer graphene, giving rise to transmission enhancement of a single-cycle THz pulse when the incident THz peak electric field is increased. This transmission enhancement is attributed to reduced photoconductivity, due to saturation effects in the field-induced current and increased intraband scattering rates arising from transient heating of electrons. We have developed a tight-binding model of the response using the length gauge interaction Hamiltonian that provides good qualitative agreement. The model fully accounts for the nonlinear response arising from the linear dispersion energy spectrum in graphene. The results reveal a strong dependence of the scattering time on the THz field, which is at the heart of the observed nonlinear response.