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Investigations into nanometer scale surface opto-electro-mechanical coupling

Abstract

We have used scanning tunneling microscopy and spectroscopy to investigate electro-mechanical coupling in two different nanoscale systems coupled to a condensed matter environment - single molecules, where we observe light induced conformational changes (photoisomerization), and graphene, where we observe conformationally controlled pseudo gauge fields.

We have observed the effects of molecule-surface and molecule-molecule coupling in photoisomerization of TTB-Azobenzene molecules on the Au(111) surface. In addition, through measurement of the photoisomerization cross section of surface bound molecules and comparing the chirality of the initial and final products of the reaction, we have gained knowledge of the likely pathways. Our studies of graphene films catalytically grown on the Pt(111) surface have found strain-induced pseudo Landau levels, which are a unique consequence of how graphene's electronic structure interacts with the local environment. These studies have allowed us to gain insight into the quantitative and qualitative ways in which the environment affects electro-mechanical coupling of nanoscale structures.

Single molecule photoisomerization and strain-induced effects serve as complementary examples of electro-mechanical coupling, since in the former case the position of the molecule's constituent atoms is affected via electric fields, while in the latter the position of the constituent atoms modifies the electrical properties of the film.

The combination of these two effects, e.g. by depositing photoswitching molecules on a gateable and strainable graphene membrane, may open the door to new applications and enable better control of matter at the nanoscale.

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