2021 Fiscal Year Research-status Report
Development of Magnetic Microscopy using RF Photon Assisted Tunneling between Superconductor Electrodes
| Project/Area Number |
21K04873
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| Research Institution | Tohoku University |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
米田 忠弘 東北大学, 多元物質科学研究所, 教授 (30312234)
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| Project Period (FY) |
2021-04-01 – 2024-03-31
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| Keywords | SC-PAT / IETS / TbPc / YSR |
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| Outline of Annual Research Achievements |
We aimed to develop a detection technique using the Super Conductor Photo Assisted Tunneling (SC-PAT) to obtain the information of the spin properties with atomic scale resolution. For that purpose, we investigated the spin properties of the terbium phthalocyanine (TbPc2) species and its fragments adsorbed on superconductor NbSe2 surface using scanning tunneling microscopy and spectroscopy. We deposited TbPc2 species on the surface of the superconductor NbSe2. In the STM image we found the robust TbPc2 and its fragments (TbPc, Pc) on the NbSe2 surface. We measured Yu-Shiba-Rusinov (YSR) states caused by the interaction between the superconducting state and magnetic impurity for the TbPc2 and TbPc species at below 1 K. Inelastic tunneling spectroscopy (IETS) for the spin excitation at sub 1 K were measured to detect spin properties when magnetic impurities interact weakly with the substrate and caused no YSR. In addition, the exchange interaction energy (Eex) between the spins of the radical ligand (Pc) and the center 4f metal atom (Tb3+) is determined by using the IETS technique. Eex is a critical parameter that determines the blocking temperature below which it behaves as SMM. We detected high precision sub millielectronvolt spatial energy variation of the Eex within the single molecule which are attributed to the bonding configuration of TbPc.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
SC-PAT microscopy is expected to detect the difference in spin chemical environment with atomic resolution. To develop that, a clear understanding of the spin properties using usual STM and STS was our primary goal. We could achieve the primary goal more smoothly than planned. Co-investigator Prof Tadahiro Komeda is highly experienced for the STM and STS techniques for spin detection and have nice experimental facilities. Although there were trouble due to covid situation but the goal could be achieved smoothly due to smooth operations in experimental facilities.
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| Strategy for Future Research Activity |
We successfully determined the exchange interaction energy (Eex) between the spins of the radical ligand (Pc) and the center 4f metal atom (Tb3+) by using the IETS technique. We found that Eex is very sensitive to the bonding configuration of TbPc molecules with the substrate. we detected the high precision sub millielectronvolt spatial energy variation of the Eex within the single molecule which are attributed to the slight change in local spin environment. The difference in bonding configuration can cause the different coupling between the RF and modified SC state during photon assisted tunneling. In future experiments, we will deploy the RF in the tunnel junction by superimposing RF over STM bias line and measure the dI/dV with the variation of RF power. As we detected the spatial variation of Eex within the molecule, we expect to detect similar variation while using SC-PAT. We can utilize our current result to build the SC-PAT system using STM.
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