2020 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 / Resonator / Josephson Junction / Majorana / Andreev Bound States |
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| Outline of Annual Research Achievements |
We performed our first studies of InAs nanowires flip-chipped onto Niobium resonators fabricated on sapphire substrates. These devices improve our Q-factor with internal Q~400,000 and will thus increase the sensitivity of the readout of states. The flip-chip technique can now be used to study devices on any substrate, significantly simplifying fabrication by separating the resonator processing from the rf-SQUID. In addition, we succeed our first dispersive readout of a HgTe Josephson junction rf-SQUID flip-chipped onto a resonator circuit. A fabrication method is also developed to produce asymmetric SQUID devices with the HgTe junctions using a conventional Ag nanowire junction as a high critical current shunt. Finally, we characterize in DC transport new InAs devices with a full-shell of epitaxial Aluminium, in which flux tuning of the bound state spectrum through the Little Parks effect for an axial magnetic field is predicted to allow topological states for a relatively low magnetic field. The characterization of these devices paves the way for the study in cavities in FY2021.
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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
The pandemic causes a delay in studies on both nanowire and HgTe work due to shutdown of measurement systems in RIKEN as well as the labs of collaborators who grow material and process devices used in this project. Despite these issues some research goals are achieved albeit at a slower pace. The bismuth nanowire system despite being successful in the fabrication of Josephson junctions will not be studied in the cavity coupled devices due to poor characteristics for the junctions fabricated with in-situ superconducting contacts and a lack of convincing signatures for the topological surface states that we seek.
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| Strategy for Future Research Activity |
Work in FY2021 will focus primarily on measurements of the resonator coupled Aluminium epitaxial full-shell InAs nanowires using resonators suitable for high magnetic fields developed in FY2019 and 2020. The bismuth nanowire system despite being successful in the fabrication of Josephson junctions will not be studied in the cavity coupled devices due to poor characteristics for the junctions fabricated with in-situ superconducting contacts and a lack of convincing signatures for the topological surface states. A successful initial study of HgTe based rf-SQUIDs suitable for coupling with cavities using a flip-chip technique was completed in FY2020. In this FY the HgTe study will be expanded to include pulsed measurements suitable for probing the quasi-particle poisoning in this system.
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Research Products
(3 results)
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[Journal Article] Fully in situ Nb/InAs-nanowire Josephson junctions by selective-area growth and shadow evaporation2021
Author(s)
Pujitha Perla, H. Aruni Fonseka, Patrick Zellekens, Russell Deacon, Yisong Han, Jonas Kolzer, Timm Morstedt, Benjamin Bennemann, Abbas Espiari, Koji Ishibashi, Detlev Grutzmacher, Ana M. Sanchez, Mihail Ion Lepsa and Thomas Schapers
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Journal Title
Nanoscale Advances
Volume: 3
Pages: 1413-1421
DOI
Peer Reviewed / Open Access / Int'l Joint Research
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[Journal Article] Hard-Gap Spectroscopy in a Self-Defined Mesoscopic InAs/Al Nanowire Josephson Junction2020
Author(s)
Patrick Zellekens, Russell Deacon, Pujitha Perla, H. Aruni Fonseka, Timm Morstedt, Steven A. Hindmarsh, Benjamin Bennemann, Florian Lentz, Mihail I. Lepsa, Ana M. Sanchez, Detlev Grutzmacher, Koji Ishibashi, and Thomas Schapers
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Journal Title
PHYSICAL REVIEW APPLIED
Volume: 14
Pages: 054019
DOI
Peer Reviewed / Int'l Joint Research
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