Nature Communications (Oct 2023)

Evidence of unconventional superconductivity on the surface of the nodal semimetal CaAg1−x Pd x P

  • Rikizo Yano,
  • Shota Nagasaka,
  • Naoki Matsubara,
  • Kazushige Saigusa,
  • Tsuyoshi Tanda,
  • Seiichiro Ito,
  • Ai Yamakage,
  • Yoshihiko Okamoto,
  • Koshi Takenaka,
  • Satoshi Kashiwaya

DOI
https://doi.org/10.1038/s41467-023-42535-5
Journal volume & issue
Vol. 14, no. 1
pp. 1 – 6

Abstract

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Abstract Surface states of topological materials provide extreme electronic states for unconventional superconducting states. CaAg1−x Pd x P is an ideal candidate for a nodal-line Dirac semimetal with drumhead surface states and no additional bulk bands. Here, we report that CaAg1−x Pd x P has surface states that exhibit unconventional superconductivity (SC) around 1.5 K. Extremely sharp magnetoresistance, tuned by surface-sensitive gating, determines the surface origin of the ultrahigh-mobility “electrons.” The Pd-doping elevates the Fermi level towards the surface states, and as a result, the critical temperature (T c) is increased up to 1.7 K from 1.2 K for undoped CaAgP. Furthermore, a soft point-contact study at the surface of Pd-doped CaAgP proved the emergence of unconventional SC on the surface. We observed the bell-shaped conductance spectra, a hallmark of the unconventional SC. Ultrahigh mobility carriers derived from the surface flat bands generate a new class of unconventional SC.