Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 28: THz Physics

HL 28.3: Talk

Monday, March 14, 2011, 18:00–18:15, POT 51

Nanotube Transisors as Quantum Cavity for Terahertz Plasmons — •Diego Kienle — Theoretische Physik I, Universität Bayreuth, 95440 Bayreuth

Since their discovery in 1990, carbon nanotubes (NTs) are believed to be one potential candidate to replace silicon- based electronics due to their exceptional electronic properties. Much effort has been invested in understanding electronic transport at DC, whereas their high-frequency (AC) properties are less explored. In this talk, we employ a newly developed theory for self-consistent AC quantum transport using Non-Equilibrium Green functions and study the AC response of NT transistors in terms of their dynamic conductance with the AC signal applied at the gate terminal. In the ON state, the conductance exhibits pronounced divergent peaks at terahertz frequencies, which are attributed to plasmon excitations. In the OFF-state such collective excitations are suppressed, since the dynamic coherence between the single-particle states is destroyed due to the reflection of electrons at the gate controlled potential barriers. In this case, the AC conductance is oscillatory - a signature of the single-particle excitation spectrum. Importantly, the plasmonic excitations are only captured if the self-consistent charge-potential feedback is an integral part of the AC theory. Higher-order plasmon modes can be excited by varying the length of the NT and thus allows to tune the plasmonic excitation spectrum. [1] D. Kienle and F. Leonard, Phys. Rev. Lett. 103, 026601 (2009). [2] D. Kienle, M. Vaidyanathan, and F. Leonard, Phys. Rev. B 81 115455 (2010).