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

The breaking of the space inversion symmetry at surfaces and interfaces leads to the Rashba-type spin-orbit coupling (SOC) in 2D materials, which can strongly affect superconductivity [1]. In this talk, I will focus on crystalline atomic-layer indium on silicon surfaces with a clear spin-splitting of the Fermi surface and in-plane spin polarizations in the momentum space [2,3]. Our electron transport measurements under ultrahigh vacuum environment reveal that its in-plane critical magnetic field exceeds the Pauli limit by a factor of 3-4 at zero temperature. Through quantitative analysis, we conclude that elastic scattering among spin-momentum-locked electronic states serves as an effective spin-orbit scattering, thereby strongly suppressing the paramagnetic pair-breaking effect [4]. The mechanism is referred to as dynamic spin-momentum locking, which is contrasted to static spin-valley locking in 2D superconductors with Zeeman-type SOC [5].

References
[1] T. Uchihashi, Supercond. Sci. Technol. 30, 013002 (2017) [2017 highlight].
[2] T. Uchihashi et al., Phys. Rev. Lett. 107, 207001 (2011) [Editors’ Suggestion/ Physics].
[3] U. Kobayashi et al., submitted.
[4] S. Yoshizawa et al., submitted.
[5] J. M. Lu et al., Science 350, 1353 (2015); Y. Saito et al. Nat. Phys. 12, 144 (2016).