High Orbital-Moment Cooper Pairs by Crystalline Symmetry Breaking

Abstract

The pairing structure of superconducting materials is regulated by the point group symmetries of the crystal. The spin-singlet multiorbital superconductivity of materials with unusually low crystalline symmetry content can host even-parity (s-wave) Cooper pairs with high orbital moment. The lack of mirror and rotation symmetries makes pairing states with quintet orbital angular momentum symmetry-allowed. A remarkable fingerprint of this type of pairing state is provided by a nontrivial superconducting phase texture in momentum space with π-shifted domains and walls with anomalous phase winding. The pattern of the quintet pairing texture is shown to depend on the orientation of the orbital polarization and the strength of the mirror and/or rotation symmetry breaking terms. Such a momentum dependent phase makes Cooper pairs with net orbital component suited to design orbitronic Josephson effects. This study discusses how an intrinsic orbital dependent phase can set out anomalous Josephson couplings by employing superconducting leads with nonequivalent breaking of crystalline symmetry.