Abstract
Recent experiments show the spontaneous breaking of rotational symmetry in the superconducting topological insulators ( represents Cu, Sr, or Nd), suggesting that the pairing belongs to a two-dimensional representation of the symmetry group of the crystal. Motivated by this progress, we construct an exhaustive list of possible two-component pairings of the superconductors, both for the odd-parity representation and for the even-parity representation. Starting from a tight-binding model for the normal phase of and , we firstly construct the pairing channels in the spin-orbital basis, up to second-nearest-neighbor pairing correlations in the basal plane. We then infer the properties of these pairings by transforming them to the band (pseudospin) basis for the conduction band. A comparison with the experiments leads to several multichannel pairings as promising pairings for superconductors. Besides a nematic and time-reversal symmetric pairing combination, the other pairings that we have identified are chiral and nematic at the same time, which may be nonunitary and have a spontaneous magnetization. A complementary set of experiments are proposed to identify the true pairing symmetries of these superconductors and their evolution with the doping concentration .
- Received 11 December 2018
- Revised 5 March 2019
DOI:https://doi.org/10.1103/PhysRevB.99.214507
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