Abstract-Observation of terahertz-induced magnetooscillations in graphene

Erwin Mönch, Denis A. Bandurin, Ivan A. Dmitriev, Isabelle Y. Phinney, Ivan Yahniuk, Takashi Taniguchi, Kenji Watanabe, Pablo Jarillo-Herrero, Sergey D. Ganichev

https://pubs.acs.org/doi/pdf/10.1021/acs.nanolett.0c01918#

When high-frequency radiation is incident upon graphene subjected to a perpendicular magnetic field, graphene absorbs incident photons by allowing transitions between nearest LLs that follow strict selection rules dictated by angular momentum conservation. Here we show a qualitative deviation from this behavior in high-quality graphene devices exposed to terahertz (THz) radiation. We demonstrate the emergence of a pronounced THz-driven photoresponse, which exhibits low-field magnetooscillations governed by the ratio of the frequency of the incoming radiation and the quasiclassical cyclotron frequency. We analyze the modifications of generated photovoltage with the radiation frequency and carrier density and demonstrate that the observed photoresponse shares a common origin with microwave-induced resistance oscillations previously observed in GaAs-based heterostructures, yet in graphene, it appears at much higher frequencies and persists above liquid nitrogen temperatures. Our observations expand the family of radiation-driven phenomena in graphene, paving the way for future studies of nonequilibrium electron transport.

Abstract-Observation of terahertz-induced magnetooscillations in graphene

Erwin Mönch, Denis A. Bandurin, Ivan A. Dmitriev, Isabelle Y. Phinney, Ivan Yahniuk, Takashi Taniguchi, Kenji Watanabe, Pablo Jarillo-Herrero, Sergey D. Ganichev

https://arxiv.org/abs/2005.01118

When high-frequency radiation is incident upon graphene subjected to a perpendicular magnetic field, graphene absorbs incident photons by allowing transitions between nearest LLs that follow strict selection rules dictated by angular momentum conservation. Here we show a qualitative deviation from this behavior in high-quality graphene devices exposed to terahertz (THz) radiation. We demonstrate the emergence of a pronounced THz-driven photoresponse, which exhibits low-field magnetooscillations governed by the ratio of the frequency of the incoming radiation and the quasiclassical cyclotron frequency. We analyze the modifications of generated photovoltage with the radiation frequency and carrier density and demonstrate that the observed photoresponse shares a common origin with microwave-induced resistance oscillations previously observed in GaAs-based heterostructures, yet in graphene, it appears at much higher frequencies and persists above liquid nitrogen temperatures. Our observations expand the family of radiation-driven phenomena in graphene and offer potential for the development of novel optoelectronic devices.

Abstract-Terahertz Photogalvanic Spectroscopy of Three Dimensional Topological Insulators

Helene Plank, Sergey D. Ganichev

https://128.84.21.199/abs/1801.04865

The paper overviews experimental and theoretical studies of photogalvanic effects induced in BiSbTe- based three dimensional topological insulators by polarized terahertz radiation. We present the state-of-the-art of this subject, including most recent and well-established results. We discuss a phenomenological theory based on symmetry arguments and models illustrating the photocurrents origin. We give a brief glimpse of the underlying microscopic theory, as well as an overview of the main experimental results.

Abstract-Terahertz electric field driven electric currents and ratchet effects in graphene

Sergey D. Ganichev, Dieter Weiss, Jonathan Eroms

(Submitted on 17 Oct 2017)

https://arxiv.org/abs/1710.06243#

Terahertz field induced photocurrents in graphene were studied experimentally and by microscopic modeling. Currents were generated by cw and pulsed laser radiation in large area as well as small-size exfoliated graphene samples. We review general symmetry considerations leading to photocurrents depending on linear and circular polarized radiation and then present a number of situations where photocurrents were detected. Starting with the photon drag effect under oblique incidence, we proceed to the photogalvanic effect enhancement in the reststrahlen band of SiC and edge-generated currents in graphene. Ratchet effects were considered for in-plane magnetic fields and a structure inversion asymmetry as well as ratchets by non-symmetric patterned top gates. Lastly, we demonstrate that graphene can be used as a fast, broadband detector of terahertz radiation.

Abstract-Terahertz split-ring metamaterials as transducers for chemical sensors based on conducting polymers: a feasibility study with sensing of acidic and basic gases using polyaniline chemosensitive layer

Christoph Drexler, 

Tatiana V. Shishkanova, 

Christoph Lange, 

Sergey N. Danilov, 

Dieter Weiss,

Sergey D. Ganichev, 

Vladimir M. Mirsky

http://link.springer.com/article/10.1007/s00604-014-1263-0
We report on the first application of terahertz metamaterials acting as transducers for chemical sensors based on conducting polymers. In our feasibility study aimed at sensing of gaseous hydrochloric and ammonia, a two-dimensional sensor metamaterial consisting of an array of split-ring resonators on the surface of undoped silicon wafer was prepared. The surface of the resonator was coated with a 150-μm layer of polyaniline. Binding of hydrogen chloride to polyaniline leads to distinct changes in the resonance frequency of the metamaterial. Measurements can be performed both in the reflection and transmission mode. A numerical simulation of the response revealed an increase of both the real and the imaginary components of the dielectric function of the polyaniline film. These changes are attributed to the transition from emaraldine base to emeraldine salt. The results demonstrate a new approach for formation of highly sensitive transducers for chemical sensors.