Symmetry-controlled multi-gap superconductivity and higher-order topological phases of MoTe2

초록

The transition-metal dichalcogenide MoTe2 has been proposed as an ideal platform to intertwine superconductivity with band topology, yet a key experiment—tracking how its properties evolve across a pressure-tuned structural and topological phase transition—has remained elusive. Here, we map the superconducting landscape across these high-pressure regimes from the noncentrosymmetric type-II Weyl semimetal Td phase to the centrosymmetric 1T′ phase using surface-sensitive soft point-contact Andreev spectroscopy combined with quantitative theoretical analysis. In the Td phase, our spectra consistently reveal two distinct superconducting gaps that remain resolvable under an external magnetic field, implying robust and pressure-independent multi-gap superconductivity consistent with muon-spin-rotation evidence for two s-wave gaps at ambient pressure. In the 1T′ phase, reached by pressure along a topological pathway that connects the Weyl to the higher-order topological phase, we observe an s + p-wave surface response whose p-wave component follows the s-wave gap in temperature and is rapidly suppressed by a magnetic field—fingerprints of proximity-induced p-wave pairing between a bulk s-wave superconducting band and second-order topological surface states. This phenomenology aligns with theoretical analysis showing that the Td phase hosts type-II Weyl points, whereas the 1T′ phase realizes a higher-order topological insulator arising from double-band inversion. Finally, we further propose that the resulting higher-order hinge boundary channels provide a natural route toward potential zero-energy Majorana corner modes under the observed s + p-wave proximity pairing, suggesting MoTe2 as an intrinsic, pressure-tunable platform for multi-gap and s + p-wave topological superconductivity.

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