Two-dimensional superconductivity with unconventional magnetotransport in PtPb4 single crystals: A nonsymmorphic symmetry-protected topological superconductor

Abstract

This study presents a new nonsymmorphic symmetry-protected topological phase, as well as a two-dimensional (2D) surface topological superconductivity on PtPb4 surface. The bulk superconductivity of PtPb4 exhibited characteristic of a conventional moderately-coupled Bardeen–Cooper–Schrieffer nonideal type-II superconductor. Nevertheless, the superconductivity investigated via electrical transport exhibited anisotropic properties of 2D nature, verified through a Berezinsky-Kosterlitz-Thouless transition and 2D-like vortex dynamics in mixed-state transports. The obtained activation energy U(H), critical current density Jc(T,H), and scaling of pinning forces for Fp(H) for PtPb4 showed a relatively weak vortex pinning in PtPb4, accompanied by a crossover of the flux-line lattice from elastic relaxation to shear deformation. In the normal state, PtPb4 revealed nontrivial quantum interference transports with a crossover from weak-antilocalization- to weak-localization-dominated transverse magnetoresistance (TMR) in the low-field region, demonstrating the presence of topological surface states on PtPb4. Besides, the violation of Kohler's rule with a power-law exponent value of 1.4 also revealed a nontrivial MR characteristic of PtPb4. The pronounced exotic TMR characteristic confirmed that PtPb4 indeed hosts topological surface states, driven by a new nonsymmorphic symmetry-protected topological phase. All results are summarized in a constructed phase diagram of PtPb4 in the H-T plane, displaying different regimes of transport. The observed 2D superconductivity, as well as nontrivial quantum-interference transports, can be attributed to the dispersion of topological Dirac-like surface band in PtPb4. Our findings provide robust support for the emergence of a new nonsymmorphic symmetry-protected topological phase on the PtPb4 surface. Thus, PtPb4 is one of the few reported nonsymmorphic symmetry-protected topological superconductors, paving the way for the development of superconducting quantum computation.

Source-reported materials — not catalogue approval

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