Quantum Near-Field Effects in Hybrid Carbon Nanotube Systems

Abstract

Physical understanding of near-field processes in complex hybrid nanostructures of reduced dimensionality is a natural prerequisite for the development of future generation advanced nanomaterials and devices. I present two examples of how the near-field processes can drastically affect optical and transport properties of hybrid carbon nanotube structures. First is the Surface Enhanced Raman Scattering (SERS) effect for a two-level atomic system (TLS) coupled to a low-energy interband plasmon resonance of a carbon nanotube (CN) [1]. Here, the SERS comes about as a strong-coupling near-field effect in which the local-field enhancement occurs due to the interband plasmon excitation when the TLS is located near the CN surface and its transition energy matches a CN local photonic DOS resonance. Previously, most of the applications of CNs to enhance the Raman scattering have been to decorate them with metallic nanoparticles, to use metal plasmons as spectroscopic enhancers with CNs only serving as their supporters [2,3]. Here, individual CNs are shown to result in the SERS effect due to their intrinsic interband plasmon modes [1]. The effect may be used to detect individual atomic type objects trapped near nanotubes. More advanced applications may include highly efficient CN based SERS substrates for single molecule/atom/ion detection, precision spontaneous emission control, and quantum optical manipulation. Second is the plasmon mediated electron transport in hybrid metal-semiconductor CN systems composed of single wall semiconducting CNs with encapsulated metallic atomic wires (AWs) [4]. Encapsulating metallic wires of just one atom thick into a single wall CN, metallic or semiconducting, is known to drastically alter the transport properties of the compound hybrid system [5]. Our theory and numerical simulations predict generic Fano resonances in charge transfer through the hybrid metal-semiconductor CN system, whereby the strong plasmon mediated AW-CN near-field interaction blocks some of the pristine AW transmission band channels to open up new coherent channels in the CN bandgap outside the AW transmission band [4]. This effect can be used to optimize charge transfer in hybrid nanodevices built on metal-semiconductor nanotube systems. I.V.B. acknowledges the US DOE grant support (DE-SC0007117). Part of this work (electron transport) was done in collaboration with M.F.Gelin of TU-Munich, Germany, whose visit to North Carolina Central University was sponsored by the US NSF grant ECCS-1306871.