Abstract-Tight-Binding Terahertz Plasmons in Chemical-Vapor-Deposited Graphene

Andrey Bylinkin, Elena Titova, Vitaly Mikheev, Elena Zhukova, Sergey Zhukov, Mikhail Belyanchikov, Mikhail Kashchenko, Andrew Miakonkikh, and Dmitry Svintsov

https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.11.054017

Transistor structures comprising graphene and subwavelength metal gratings hold great promise for plasmon-enhanced terahertz detection. Despite considerable theoretical effort, little experimental evidence for terahertz plasmons in such structures has been found so far. Here we report an experimental study of plasmons in graphene-insulator-grating structures using Fourier-transform spectroscopy in the 5–10-THz range. The plasmon resonance is clearly visible above the Drude absorption background even in chemical-vapor-deposited graphene with low carrier mobility of approximately ${10}^3$ ${\mathrm{cm}}^2/$V s. We show that the plasmon lifetime exceeds the transport relaxation time extracted from dc mobility, and argue that the former is weakly sensitive to scattering by grain boundaries and macroscopic defects inherent in chemical-vapor-deposited samples. We find that a grating coupler close to graphene strongly modifies the plasmon spectrum, which is determined by metal stripe width but not by grating period. We present a simple theory of grating-coupled two-dimensional plasmons, akin to the tight-binding theory of electrons in solids, that reproduces the observed resonant frequencies without fitting parameters. Our results demonstrate the prospect of large-area commercially available graphene for resonant terahertz detectors.

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Abstract-Resonant terahertz detection using graphene plasmons

Denis A. Bandurin, Dmitry Svintsov, Igor Gayduchenko, Shuigang G. Xu, Alessandro Principi, Maxim Moskotin, Ivan Tretyakov, Denis Yagodkin, Sergey Zhukov, Takashi Taniguchi, Kenji Watanabe, Irina V. Grigorieva, Marco Polini, Gregory N. Goltsman, Andre K. Geim,  Georgy Fedorov

https://www.nature.com/articles/s41467-018-07848-w

Plasmons, collective oscillations of electron systems, can efficiently couple light and electric current, and thus can be used to create sub-wavelength photodetectors, radiation mixers, and on-chip spectrometers. Despite considerable effort, it has proven challenging to implement plasmonic devices operating at terahertz frequencies. The material capable to meet this challenge is graphene as it supports long-lived electrically tunable plasmons. Here we demonstrate plasmon-assisted resonant detection of terahertz radiation by antenna-coupled graphene transistors that act as both plasmonic Fabry-Perot cavities and rectifying elements. By varying the plasmon velocity using gate voltage, we tune our detectors between multiple resonant modes and exploit this functionality to measure plasmon wavelength and lifetime in bilayer graphene as well as to probe collective modes in its moiré minibands. Our devices offer a convenient tool for further plasmonic research that is often exceedingly difficult under non-ambient conditions (e.g. cryogenic temperatures) and promise a viable route for various photonic applications.