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Idzuchi H, Pientka F, Huang KF, Harada K, Gül Ö, Shin YJ, Nguyen LT, Jo NH, Shindo D, Cava RJ, Canfield PC, Kim P. Unconventional supercurrent phase in Ising superconductor Josephson junction with atomically thin magnetic insulator. Nat Commun 2021; 12:5332. [PMID: 34504077 PMCID: PMC8429564 DOI: 10.1038/s41467-021-25608-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 08/22/2021] [Indexed: 11/23/2022] Open
Abstract
In two-dimensional (2D) NbSe2 crystal, which lacks inversion symmetry, strong spin-orbit coupling aligns the spins of Cooper pairs to the orbital valleys, forming Ising Cooper pairs (ICPs). The unusual spin texture of ICPs can be further modulated by introducing magnetic exchange. Here, we report unconventional supercurrent phase in van der Waals heterostructure Josephson junctions (JJs) that couples NbSe2 ICPs across an atomically thin magnetic insulator (MI) Cr2Ge2Te6. By constructing a superconducting quantum interference device (SQUID), we measure the phase of the transferred Cooper pairs in the MI JJ. We demonstrate a doubly degenerate nontrivial JJ phase (ϕ), formed by momentum-conserving tunneling of ICPs across magnetic domains in the barrier. The doubly degenerate ground states in MI JJs provide a two-level quantum system that can be utilized as a new dissipationless component for superconducting quantum devices. Our work boosts the study of various superconducting states with spin-orbit coupling, opening up an avenue to designing new superconducting phase-controlled quantum electronic devices. Van der Waals structures provide a new platform to explore novel physics of superconductor/ferromagnet interfaces. Here, NbSe2 Josephson junction with Cr2Ge2Te6 enables non-trivial Josephson phase by spin-dependent interaction, boosting the study of superconducting states with spin-orbit coupling and phase-controlled quantum electronic device.
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Affiliation(s)
- H Idzuchi
- Department of Physics, Harvard University, Cambridge, MA, USA.,WPI Advanced Institute for Materials Research and Center for Science and Innovation in Spintronics, Tohoku University, Sendai, Japan
| | - F Pientka
- Department of Physics, Harvard University, Cambridge, MA, USA.,Institut für Theoretische Physik, Goethe-Universität, Frankfurt am Main, Germany
| | - K-F Huang
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - K Harada
- Center for Emergent Matter Science (CEMS), RIKEN, Hatoyama, Saitama, Japan
| | - Ö Gül
- Department of Physics, Harvard University, Cambridge, MA, USA
| | - Y J Shin
- Department of Physics, Harvard University, Cambridge, MA, USA.,Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY, USA
| | - L T Nguyen
- Department of Chemistry, Princeton University, Princeton, NJ, USA
| | - N H Jo
- Department of Physics and Astronomy, Iowa State University, Ames, IA, USA.,Ames Laboratory, Iowa State University, Ames, IA, USA
| | - D Shindo
- Center for Emergent Matter Science (CEMS), RIKEN, Hatoyama, Saitama, Japan
| | - R J Cava
- Department of Chemistry, Princeton University, Princeton, NJ, USA
| | - P C Canfield
- Department of Physics and Astronomy, Iowa State University, Ames, IA, USA.,Ames Laboratory, Iowa State University, Ames, IA, USA
| | - P Kim
- Department of Physics, Harvard University, Cambridge, MA, USA.
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