Perfect spin and/or valley triplet pairing states in an antiferromagnetic-silicene/superconductor hybrid structure

We theoretically propose an antiferromagnetic silicene/superconductor hybrid structure, which unveils unconventional Andreev reflections (ARs) due to the Rashba spin-orbit and interface couplings. They are characterized by perfect spin- or/and valley-triplet pairing states with the spin or/and valley being fully polarized. Of the most striking is the spin-valley-triplet (intravalley equal-spin) AR induced by the combination of spin-flip and valley-mixing scatterings, which is an alternative pairing process. The tunability of spin and valley polarizations in antiferromagnetic silicene enables a spin-valley pairing switch between three types of triplet (intervalley equal-spin, intravalley opposite-spin, and intravalley equal-spin) pairing AR processes. It is also demonstrated that the corresponding subgap conductance spectra for each type exhibits distinct characteristic features, which can be directly tested experimentally using scanning tunnel microscope measurements and/or point-contact spectroscopy. Our findings may pave the way for the application of silicene in spin-valleytronics.