Crossed Andreev Reflection in Zigzag Phosphorene Nanoribbon Based Ferromagnet/Superconductor/Ferromagnet Junctions

We study the crossed Andreev reflection in zigzag phosphorene nanoribbon based ferromagnet/superconductor/ferromagnet junction. Only edge states, which are entirely detached from the bulk gap, involved in the transport process. The perfect crossed Andreev reflection, with the maximal nonlocal conductance −2e 2 /h, is addressed by setting the chemical potentials of the leads properly. At this situation, the local Andreev reflection and the electron tunneling are completely eliminated, the incoming electrons can only be reflected as electrons or transmitted as holes, corresponding to the electron reflection and the crossed Andreev reflection respectively. The nonlocal conductance oscillates periodically with the length and the chemical potential of the superconductor. Our study shows that the phosphorene based junction can be used as the quantum device to generate entangled-electrons.

Hydrogen-impurity-induced conductance peaks in constriction type Josephson junctions

We studied hydrogen (H) and deuterium (D) impurity effects of superconducting Josephson current flowing through the superconductor-constriction-superconductor Josephson junctions (ScS-JJ). When H or D impurities are adsorbed on the surface of the ScS-JJ prepared by niobium (Nb) or lead (Pb), many spike-like peaks with almost the same spacing appear inside the superconducting gap in addition to anomalies owing to the multiple Andreev reflection in the differential conductance spectra. The spacing between the adjacent peaks is independent of the temperature variation. These indicate that H or D impurities adsorbed on the JJ are sources of noise for the Josephson current.

Evidence for anisotropic spin-triplet Andreev reflection at the 2D van der Waals ferromagnet/superconductor interface

Fundamental symmetry breaking and relativistic spin–orbit coupling give rise to fascinating phenomena in quantum materials. Of particular interest are the interfaces between ferromagnets and common s-wave superconductors, where the emergent spin-orbit fields support elusive spin-triplet superconductivity, crucial for superconducting spintronics and topologically-protected Majorana bound states. Here, we report the observation of large magnetoresistances at the interface between a quasi-two-dimensional van der Waals ferromagnet Fe0.29TaS2 and a conventional s-wave superconductor NbN, which provides the possible experimental evidence for the spin-triplet Andreev reflection and induced spin-triplet superconductivity at ferromagnet/superconductor interface arising from Rashba spin-orbit coupling. The temperature, voltage, and interfacial barrier dependences of the magnetoresistance further support the induced spin-triplet superconductivity and spin-triplet Andreev reflection. This discovery, together with the impressive advances in two-dimensional van der Waals ferromagnets, opens an important opportunity to design and probe superconducting interfaces with exotic properties.