Ising pairing in few-layer stanene and high-Tc Josephson junctions of twisted bicrystalline cuprate

In this talk, I will present our recent studies on the emergent superconductivity in few-layer stanene [1][2] as well as Josephson effect in c-axis twisted bicrystalline cuprate [3]. In the first part, I will report the discovery of superconductivity in few-layer stanene—ultrathin gray tin (111). Few-layer stanene not only exhibits two-dimensional superconductivity but also topologically non-trivial band structures [1]. Furthermore, they host enhanced in-plane upper critical fields that greatly exceed the conventional limit. We propose that this anomalous behavior stems from a novel type of Ising pairing [2]. In the second part, we realize a high-Tc Josephson junction by artificially stacking two Bi2Sr2CaCu2O8+δ (BSCCO) thin flakes on top of each other. We demonstrate that the Josephson current solely arises from the coupling between the rotated double copper-oxide planes. Notably, the Josephson coupling strength reaches the same level for different twist angles, indicative of an isotropic superconducting order parameter [3]. References[1] M. Liao et al., Nat. Phys. 14, 344 (2018).[2] J. Falson et al., Science 367, 1454 (2020).[3] Y. Zhu et al., Phys. Rev. X accepted.