Wednesday, July 10, 2013

1307.2394 (Y. Yang et al.)

Pairing with dominant triplet component and possible weak topological
superconductivity in BiS$_2$-based superconductors

Y. Yang, W. S. Wang, Y. Y. Xiang, Z. Z. Li, Q. H. Wang
We show that the newly discovered BiS$_2$-based superconductors may have a dominant triplet pairing component, in addition to a subdominant singlet component arising from the spin-orbital coupling. The pairing respects time-reversal symmetry. The dominant triplet gap causes gap sign changes between the spin-split Fermi pockets. Within a pocket, the gap function respects $d^*_{x^2-y^2}$-wave symmetry, where the star indicates joint spin-lattice rotations. Below the Lifshitz filling level the gap is nodelss and the superconducting state is weak topological. Above the Lifshitz points the gap becomes nodal. The dominant triplet pairing is consistent with the experimental upper critical field exceeding the Pauli limit.
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