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THz response of nonequilibrium electrons of highly doped graphene on a polar substrate

Kukhtaruk S. M.

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Abstract. 
We consider high-frequency response of a system consisting of drifting electrons in a highly doped graphene and surface polar optical phonons of a polar substrate. We obtain the dielectric function, the frequencies and the decrement/increment of cooperative plasmon–optical phonon oscillations for this interacting system. We find that the response depends significantly on the degree of nonequilibrium for the electrons. In particular, the interaction between drifting plasmons and surface polar optical phonons leads to instability of the electron subsystem due to Vavilov–Cherenkov effect. We suggest that the hybrid system, a graphene on a polar substrate, is capable of using in amplifiers or generators of THz electromagnetic radiation.

Keywords: graphene, plasmon, optical phonon, instability, dielectric function

PACS: 72.80.Vp, 73.20.Mf, 71.38.-k, 71.45.Gm, 77.22.Ch
UDC:  535.58, 535.56, 537.5
Ukr. J. Phys. Opt. 14 24-30
doi: 10.3116/16091833/14/1/24/2013
Received: 01.11.2012

Анотація. Розглянуто надвисокочастотний відгук системи дрейфуючих електронів сильно легованого графену та поверхневих оптичних фононів полярної підкладки. Для взаємодіючої системи розраховано діелектричну функцію, частоти та декремент/інкремент спільних коливань. Показано, що відгук системи суттєво залежить від ступеня нерівноважності електронів. Зокрема, взаємодія між плазмонами та поверхневими оптичними фононами приводить до дрейфової нестійкості, зумовленої ефектом Вавілова–Черенкова. Розглянуту систему можна використовувати для генерації або підсилення терагерцового електромагнітного випромінювання
 
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