Double local and double nonlocal Andreev reflections in nodal-line semimetal-superconducting heterostructures

Double local and double nonlocal Andreev reflections in a nodal-line semimetal-superconductor-nodal-line semimetal junction were investigated. We find that double Andreev reflections (the specular Andreev reflection and the retro-Andreev reflection), double normal reflections (the specular normal reflection and the retronormal reflection), double electron transmissions (the specular electron transmission and the normal electron transmission), and double crossed Andreev reflections (the specular crossed Andreev reflection and the crossed Andreev reflection) exist simultaneously when an electron incidents from the semimetal side. The transport properties of the scattering process depend on the incident angle, incident energy, and barrier height. It is found that a finite incident angle and a finite barrier height are necessary conditions for the appearance of these local and nonlocal Andreev reflections. By adjusting these parameters, the reflections and transmissions can be controlled.