Development of Single-Molecule Spin ESR-STM and a Novel Tunneling Spectroscopy Method Toward Qubit Construction

The control of spin information at the atom- or molecule-level is attracting attention for quantum information processing. Scanning tunneling microscopy (STM) can provide a feasibility study for this technique, in which the radio frequency (RF) signal plays a vital role in characterization and operation. In this article, recent studies that combine the RF signal with the STM tunneling junction will be introduced. First, we show an example of electron spin resonance (ESR) detection using STM for a single magnetic molecule adsorbed on a NaCl on Cu. An apparent increase in the tunneling current occurs when the magnetic field and RF parameters satisfy the Zeeman conditions of an unpaired orbital. Second, we analyze how the RF affects scanning tunneling spectroscopy (STS) features, whichc are quasi-particle peaks in the superconducting material. We demonstrated that the STS peak is separated by the photon-assisted tunneling process, which is applicable to a nanoscale chemical analysis.