Confined carbyne for optoelectronics and optomechanics

• Applicant: Dr. Sebastian Heeg
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 433878606

This project will establish carbyne, a one-dimensional linear chain of carbon atoms inside a carbon nanotube, as a new material system to manipulate the molecular vibrations through optomechanical interaction, and to realize a transistor on the atomic scale. I will exploit two unique properties of carbyne that arise directly from its atomic structure. Carbyne is a Peierls material which exists in a metallic phase where the atoms are connected by double bonds, and in a semiconducting phase with alternating single and triple bonds. Carbyne can be switched between the two phases by doping, which will allow me to use carbyne as a transistor channel where the current flow is controlled by changing the structural phase of carbyne. This enables a nanoscale transistor at the absolute lower size limit with a channel cross section of one atom, and differs radically from conventional transistor architectures where the current flow is controlled by doping a semiconductor. Recent theoretical works suggest to manipulate molecular vibrations (phonons) through the optomechanical interaction of a molecule with the intense light fields of a plasmonic nanostructure. This transfers the concept of optomechanical interaction between a macroscopic resonator and an optical cavity to the molecular scale, and predicts million-fold stronger optomechanical coupling rates. Phonons can then act as information carriers and allow for the study of quantum-mechanical effects in optomechanics. Current experimental realizations, however, fail due to molecular disintegration driven by the strong light fields generated by the plasmonic structures. Here, I suggest to overcome this limitation by exploiting the exceptionally high Raman scattering cross section of carbyne, the rate at which molecular vibrations are scattering inelastically by light. This reduces the field intensities required to enter the regime of optomechanical interaction and will allow me to prepare non-thermal phonon populations in carbyne. Phonon lasing and the emission of correlated photons as two of the intriguing consequences of molecular optomechanical interaction will be demonstrated.The project initially aims at exploring the phonon and excitation dynamics of confined carbyne and how these properties are influenced by the host nanotubes. I will achieve this by combining tip-enhanced, temperature-, and wavelength dependent Raman spectroscopy. Confined carbyne will be brought into a device configuration and interfaced with plasmonic structures by dielectrophoretic deposition, where the nanotube acts as a carrier system. Electrical transport measurements will verify the functionality of the carbyne transistor. The proposed project establishes confined carbyne as a new material system to study molecular optomechanics and will allow me to explore new phenomena such as the frequency conversion of light on the molecular scale.

• DFG Programme: Independent Junior Research Groups
• International Connection: Austria, Brazil, China
• Major Instrumentation: SPM Controller ; Spektrometer und CCD ; Tunable Laser
• Instrumentation Group: 1890 Optische Spektrometer (außer 180-186) ; 5091 Rasterkraft-Mikroskope ; 5700 Festkörper-Laser
• Cooperation Partners: Professor Dr. Ado Jorio; Professor Dr. Thomas Pichler; Professor Dr. Lei Shi