Dirac surface states and nature of superconductivity in noncentrosymmetric BiPd

Zhixiang Sun, Mostafa Enayat, Ana Isabel Maldonado, Calum Lithgow, Ed Yelland, Darren C. Peets, Alexander Yaresko, Andreas P. Schnyder, Peter Wahl

Research output: Contribution to journalArticlepeer-review

92 Citations (Scopus)


In non-magnetic bulk materials, inversion symmetry protects the spin degeneracy. If the bulk crystal structure lacks a centre of inversion, however, spin-orbit interactions lift the spin degeneracy, leading to a Rashba metal whose Fermi surfaces exhibit an intricate spin texture. In superconducting Rashba metals a pairing wavefunction constructed from these complex spin structures will generally contain both singlet and triplet character. Here we examine possible triplet components of the order parameter in noncentrosymmetric BiPd, combining for the first time in a noncentrosymmetric superconductor macroscopic characterization, atomic-scale ultra-low temperature scanning tunnelling spectroscopy, and relativistic first-principles calculations. While the superconducting state of BiPd appears topologically trivial, consistent with Bardeen-Cooper-Schrieffer theory with an order parameter governed by a single isotropic s-wave gap, we show that the material exhibits Dirac-cone surface states with a helical spin polarization.
Original languageEnglish
Article number6633
Number of pages6
JournalNature Communications
Publication statusPublished - 30 Mar 2015


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