Multiphase superconductivity in PdBi2

Lewis Powell; Wenjun Kuang; Gabriel Hawkins-Pottier; Rashid Jalil; John Birkbeck; Ziyi Jiang; Minsoo Kim; Yichao Zou; Sofiia Komrakova; Sarah Haigh; Ivan Timokhin; Geetha Balakrishnan; Andre K Geim; Niels Walet; Alessandro Principi; Irina V Grigorieva

doi:10.1038/s41467-024-54867-x

Multiphase superconductivity in PdBi₂

Nat Commun. 2025 Jan 2;16(1):291. doi: 10.1038/s41467-024-54867-x.

Authors

Lewis Powell^#¹, Wenjun Kuang^#^{2

3}, Gabriel Hawkins-Pottier^#², Rashid Jalil², John Birkbeck², Ziyi Jiang², Minsoo Kim², Yichao Zou⁴, Sofiia Komrakova², Sarah Haigh⁴, Ivan Timokhin², Geetha Balakrishnan⁵, Andre K Geim^{2

6}, Niels Walet², Alessandro Principi⁷, Irina V Grigorieva^{8

9}

Affiliations

¹ Department of Physics and Astronomy, University of Manchester, Manchester, UK. [email protected].
² Department of Physics and Astronomy, University of Manchester, Manchester, UK.
³ National Innovation Institute of Defense Technology, AMS, Beijing, China.
⁴ Department of Materials, University of Manchester, Manchester, UK.
⁵ Department of Physics, University of Warwick, Coventry, UK.
⁶ National Graphene Institute, University of Manchester, Manchester, UK.
⁷ Department of Physics and Astronomy, University of Manchester, Manchester, UK. [email protected].
⁸ Department of Physics and Astronomy, University of Manchester, Manchester, UK. [email protected].
⁹ National Graphene Institute, University of Manchester, Manchester, UK. [email protected].

^# Contributed equally.

Abstract

Unconventional superconductivity, where electron pairing does not involve electron-phonon interactions, is often attributed to magnetic correlations in a material. Well known examples include high-T_c cuprates and uranium-based heavy fermion superconductors. Less explored are unconventional superconductors with strong spin-orbit coupling, where interactions between spin-polarised electrons and external magnetic field can result in multiple superconducting phases and field-induced transitions between them, a rare phenomenon in the superconducting state. Here we report a magnetic-field driven phase transition in β-PdBi₂, a layered non-magnetic superconductor. Our tunnelling spectroscopy on thin PdBi₂ monocrystals incorporated in planar superconductor-insulator-normal metal junctions reveals a marked discontinuity in the superconducting properties with increasing in-plane field, which is consistent with a transition from conventional (s-wave) to nodal pairing. Our theoretical analysis suggests that this phase transition may arise from spin polarisation and spin-momentum locking caused by locally broken inversion symmetry, with p-wave pairing becoming energetically favourable in high fields. Our findings also reconcile earlier predictions of unconventional multigap superconductivity in β-PdBi₂ with previous experiments where only a single s-wave gap could be detected.