2019 Fiscal Year Annual Research Report
Microwave Spectroscopy of Hybrid Topological Systems
| Project/Area Number |
19H02548
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| Research Institution | Institute of Physical and Chemical Research |
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Principal Investigator |
ディーコン ラッセル 国立研究開発法人理化学研究所, 開拓研究本部, 専任研究員 (40552443)
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| Project Period (FY) |
2019-04-01 – 2022-03-31
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| Keywords | Topological / Josephson Junction / Andreev Bound State / Resonator / Majorana |
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| Outline of Annual Research Achievements |
We developed a fabrication process to produce Josephson junction devices with epitaxial superconductors deposited in-situ within the MBE system of our collaborators (the group of Prof. Schafer in Julich, Germany). These devices with both Aluminium and Niobium superconductors were characterized in DC transport and the Aluminium devices were found to be suitable for the spectroscopic measurements in this project with sufficiently high contact transparency. We also successfully achieve the readout of single Andreev bound states in a cavity coupled InAs nanowire Josephson junction without an applied magnetic field. Through two-tone spectroscopy we are able to probe both the dispersion of the Andreev bound states and also single quasi-particle transitions between these states. It is these single particle transitions that can provide a wealth of information on the system and also may provide a route toward detection of topological states later in this project. Finally, we perform characterization of Bismuth nanowires devices fabricated without our laboratory also with in-situ deposited superconducting contacts. This study reveals good contact transparency but with transport properties dominated by a short diffusive junction and has yet to provide evidence of the sought after topological surface states.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
Progress on resonator based readout of Andreev bound states is currently running on course. Bismuth nanowires have been fabricated with a novel in-situ superconducting deposition technique to form junctions and are demonstrated to show superconducting transport with transparent junctions. However, evidence of the topological modes in Bismuth nanowires that we are interested in have not been successfully detected.
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| Strategy for Future Research Activity |
In FY2020 we will focus upon resonator spectroscopy using the high Q cavities developed in FY2019. We intend to investigate both InAs nanowires (supplied by the group of Prof. Schafer, Julich Germany) and HgTe based topological insulators (supplied by the group of Prof. Molenkamp, Wurzburg Germany). Work on our own labs Bismuth nanowire growth will be extended to consider alternative superconductors searching for a system in which selective etching may produce more control over the device geometry.
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