Mechanical and Magnetic Single-Molecule Excitations by Radio-Frequency Scanning Tunneling Microscopy

In the second half of the twentieth century, two new investigation techniques emerged that both revolutionized science and technology in their fields. The first one is (nuclear and electron) magnetic resonance (NMR, ESR), which exhibits superior energy resolution owing to the high precision of frequency measurements at resonant conditions. The second technique is scanning tunneling microscopy (STM) that has quickly established as a major investigation tool with its atomic spatial resolution. In order to benefit from both, the superior spatial resolution of the STM and the exceptional energy resolution of resonance techniques, we developed a radio-frequency (rf) STM based on a commercial low-temperature STM upgraded by a home-built rf-spectroscopic system that can be operated in active and passive modes. Here, we review recent progress in the field of rf-STM, with particular focus on our recent results on the detection and excitation of mechanical vibrations of one-dimensional molecular nanoresonators as well as of nuclear, electron, and mixed nuclear/electron spin transitions in single molecules.