Unconventional supercurrent phase in Ising superconductor Josephson junction with atomically thin magnetic insulator.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Information Science

Background:

• Two-dimensional (2D) NbSe2 lacks inversion symmetry, leading to strong spin-orbit coupling.
• This coupling forms Ising Cooper pairs (ICPs) with unique spin textures.
• Magnetic exchange can further modulate ICP spin properties.

Purpose of the Study:

• To investigate unconventional supercurrent phase in van der Waals heterostructure Josephson junctions (JJs).
• To couple NbSe2 ICPs across an atomically thin magnetic insulator (MI) barrier.
• To explore the potential of these structures for superconducting quantum devices.

Main Methods:

• Fabrication of van der Waals heterostructure Josephson junctions (JJs).
• Construction of a superconducting quantum interference device (SQUID).
• Measurement of the supercurrent phase in the MI JJ using SQUID.

Main Results:

• Demonstrated a doubly degenerate nontrivial Josephson junction (JJ) phase (ϕ).
• Observed momentum-conserving tunneling of ICPs across magnetic domains in the Cr2Ge2Te6 barrier.
• Identified doubly degenerate ground states in MI JJs.

Conclusions:

• The doubly degenerate ground states in MI JJs form a two-level quantum system.
• This system can serve as a new dissipationless component for superconducting quantum devices.
• The findings advance the study of superconducting states with spin-orbit coupling and enable new quantum electronic device designs.