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Nuclear magnetic resonance provides a wealth of information about the magnetic and nematic degrees of freedom in the iron-based superconductors. A striking observation is that the spin lattice relaxation rate is inhomogeneous with a standard deviation that correlates with the nematic susceptibility. Moreover, the spin lattice relaxation is strongly affected by uniaxial strain, and in doped samples it depends sensitively upon the history of the applied strain. These observations suggest that quenched strain fields associated with doping atoms induce a nematic glass in the iron pnictide materials. 

Abstract In two-dimensional (2D) NbSe 2 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 NbSe 2 ICPs across an atomically thin magnetic insulator (MI) Cr 2 Ge 2 Te 6 . 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.