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It has recently been pointed out that nodal noncentrosymmetric superconductors are topologically non-trivial, with the nodal rings possessing a non-zero topological charge [1]. In these systems a bulk-boundary correspondence can be developed, which guarantees the existence of a flat band of singly degenerate zero-energy states within the projection of the nodal lines onto the surface Brillouin zone. Using the quasiclassical method [2,3], we present results for the surface bound state spectra, and provide a condition for the existence of the zero-energy states in terms of the sign of the gaps. The zero-energy surface states are shown to leave distinct signatures in the tunneling conductance, which can be used as an experimental test of the order parameter symmetry.
[1] A. P. Schnyder and S. Ryu, Phys. Rev. B 84, 060504(R) (2011). [2] P. M. R. Brydon, A. P. Schnyder, and C. Timm, Phys. Rev. B 84, 020501(R) (2011). [3] A. P. Schnyder, P. M. R. Brydon, and C. Timm, Phys. Rev B 85, 024522 (2012). |
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