Atomic-layer Rashba-type superconductor protected by dynamic spin-momentum locking

Shunsuke Yoshizawa; Takahiro Kobayashi; Yoshitaka Nakata; Koichiro Yaji; Kenta Yokota; Fumio Komori; Shik Shin; Kazuyuki Sakamoto; Takashi Uchihashi

doi:10.1038/s41467-021-21642-1

arXiv · 2103.07143

Atomic-layer Rashba-type superconductor protected by dynamic spin-momentum locking

Shunsuke Yoshizawa·Takahiro Kobayashi·Yoshitaka Nakata·Koichiro Yaji·Kenta Yokota·Fumio Komori·Shik Shin·Kazuyuki Sakamoto·Takashi Uchihashi

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Abstract

Spin-momentum locking is essential to the spin-split Fermi surfaces of inversion-symmetry broken materials, which are caused by either Rashba-type or Zeeman-type spin-orbit coupling (SOC). While the effect of Zeeman-type SOC on superconductivity has experimentally been shown recently, that of Rashba-type SOC remains elusive. Here we report on convincing evidence for the critical role of the spin-momentum locking on crystalline atomic-layer superconductors on surfaces, for which the presence of the Rashba-type SOC is demonstrated. In-situ electron transport measurements reveal that in-plane upper critical magnetic field is anomalously enhanced, reaching approximately three times the Pauli limit at $T = 0$. Our quantitative analysis clarifies that dynamic spin-momentum locking, a mechanism where spin is forced to flip at every elastic electron scattering, suppresses the Cooper pair-breaking parameter by orders of magnitude and thereby protects superconductivity. The present result provides a new insight into how superconductivity can survive the detrimental effects of strong magnetic fields and exchange interactions.

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Shunsuke Yoshizawa, Takahiro Kobayashi, Yoshitaka Nakata, Koichiro Yaji, Kenta Yokota, Fumio Komori, Shik Shin, Kazuyuki Sakamoto, Takashi Uchihashi. 2021-03-12. Atomic-layer Rashba-type superconductor protected by dynamic spin-momentum locking. https://doi.org/10.1038/s41467-021-21642-1

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