[18p-Z31-1~19] 17.3 Layered materials

[18p-Z31-17] Unconventional supercurrent phase in Ising superconductor Josephson junction with atomically thin magnetic insulator

〇Hiroshi Idzuchi¹, Philip Kim² (1.Tohoku Univ., 2.Harvard Univ.)

Keywords:two-dimensional material, Josephson effect, magnetic tunnel junction

When two superconductors are connected across a ferromagnet, the spin configuration of the transferred Cooper pairs can be modulated due to magnetic exchange interaction. The resulting supercurrent can reverse its sign across the magnetic Josephson junction (JJ) . The recent rise of 2D ferromagnets (F) and superconductors (S) provides an opportunity to build JJ with an atomically thin magnetic weak link formed in all crytallined junction. Here we demonstrate Josephson phase modulation in vertically stacked S-F-S van der Waals (vdW) heterostructure, employing superconducting NbSe₂ and atomically thin magnetic insulator (MI) Cr₂Ge₂Te₆. We probe the phase of MI-JJ by constructing a SQUID based on MI JJs. We demonstrate a doubly degenerate non-trivial JJ phase, formed by momentum conserving tunneling of Ising Cooper pairs across magnetic domains in the Cr₂Ge₂Te₆ 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, including phase batteries, memories, and quantum Ratchets.