Abstract-Time resolved terahertz spectroscopy of optically pumped multilayered graphene on silicon substrate

Alexandr N. Grebenchukov,  Anton D. Zaitsev,  Petr S. Demchenko,  Mikhail G. Novoselov,  Egor V. Kornilov,  Evgeniya O. Kovalska; Anna V. Baldycheva, Mikhail K. Khodzitsky

In this work, we study infrared optical pump-induced changes in terahertz conductivity of multi-layer graphene on a silicon substrate using terahertz time-domain spectroscopy. Results indicate that the conductivity and optical parameters of investigated material strongly depend on a pumping intensity and the presence of FeCl₃molecules intercalation. The findings are helpful for determining the most optically tunable material towards designing of optically controllable terahertz devices based on new two-dimensional material beyond graphene monolayer.

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Abstract-Photon-induced Quantum Oscillations of the Terahertz Conductivity in Graphene

Ricardo Vega Monroy and Guillermo Salazar Cohen

http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.6b02488

In this work we present a theory, which is able to explain the non-monotonic decreasing behavior (observed in experimental data1-11) of the graphene terahertz conductivity with the increase of the field frequency. In this connection, the displacement of the structure of topological states inside the energy band gap, which appears in graphene due to the strong photon-electron coupling, and the narrowing of this gap, as result of electron transitions from bound photon-dressed electron states to extended states outside the energy gap driven by the field frequency, lead to a periodic change of singularities near the edge of the band gap, resulting in subtle quantum oscillations of the dynamical terahertz conductivity. This quantum contribution complements the Drude response, which fits the spectral range.

Abstract-Terahertz Conductivity of the Heavy-Fermion State in CeCoIn5

 Marc Scheffler, Thomas Weig, Martin Dressel, Hiroaki Shishido, Yuta Mizukami, Takahito Terashima, Takasada Shibauchi, Yuji Matsuda
http://arxiv.org/abs/1304.2325

The optical properties of thin films of the heavy-fermion compound CeCoIn5, which were deposited by molecular beam epitaxy onto MgF2 substrates, have been studied at frequencies 7 to 45 cm^{-1} (corresponding to 0.2 to 1.3 THz) and temperatures 2 to 300 K. We observe an electrodynamic behavior which is typical for heavy fermions, namely Drude-like conductivity with a relaxation rate at rather low frequencies. This relaxation rate increases almost linearly with temperature up to at least 30 K. The coherent heavy-fermion state, characterized by an increase of the effective mass, continuously evolves upon cooling and is not fully developed for temperatures as low as 5 K.

Abstract-Terahertz conductivity of reduced graphene oxide films

J. T. Hong, K. M. Lee, B. H. Son, S. J. Park, D. J. Park, Ji-Yong Park, Soonil Lee, and Y. H. Ahn »View Author Affiliations

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-21-6-7633

We performed time-domain terahertz (THz) spectroscopy on reduced graphene oxide (rGO) network films coated on quartz substrates from dispersion solutions by spraying method. The rGO network films demonstrate high conductivity of about 900 S/cm in the THz frequency range after a high temperature reduction process. The frequency-dependent conductivities and the refractive indexes of the rGO films have been obtained and analyzed with respect to the Drude free-electron model, which is characterized by large scattering rate. Finally, we demonstrate that the THz conductivities can be manipulated by controlling the reduction process, which correlates well with the DC conductivity above the percolation limit.