Charge Transport in Azobenzene-Based Single-Molecule Junctions

The azobenzene class of molecules has become an archetype of molecular photoswitch research, due to their simple structure and the significant difference of the electronic system between their \textit{cis} and \textit{trans} isomers. However, a detailed understanding of the charge transport for the two isomers, when embedded in a junction with electrodes is still lacking. In order to clarify this issue, we investigate charge transport properties through single Azobenzene-ThioMethyl (AzoTM) molecules in a mechanically controlled break junction (MCBJ) system at 4.2 K. Single-molecule conductance, \textit{I}-\textit{V} characteristics, and IETS spectra of molecular junctions are measured and compared with first-principles transport calculations. Our studies elucidate the origin of a slightly higher conductance of junctions with \textit{cis} isomer and demonstrate that IETS spectra of \textit{cis} and \textit{trans} forms show distinct vibrational fingerprints that can be used for identifying the isomer.[1] \\ 1. Y. Kim, A. Garcia-Lekue, D. Sysoiev, T. Frederiksen, U. Groth, E. Scheer, Phys. Rev. Lett. (accepted).