Photoinduced spin-polarized transport and controllable valley-triplet pairing states in a silicene-superconductor junction

Abstract

We theoretically investigate the spin-polarized subgap transport and valley-triplet pairing states in a silicene-superconductor junction. By using the nonequilibrium Green's function, it is found that the subgap conductance is strongly affected by the spin polarization induced by an off-resonant circularly polarized light. More importantly, the presence of valley-mixing scattering at the interface could result in a valley-triplet Andreev reflection (AR) process, where the incident electrons and reflected holes come from the same valley. We also find that the amplitude of the valley-triplet AR is controllable by tuning the intensity of the light, the position of the Fermi level, and even the interface coupling strength. Particularly, the fully valley-polarized conductance spectrum shows distinctive behaviors, which is beneficial for us to verify and detect the possible valley-triplet pairing states as well as the spin/valley polarizations in silicene. Our results may pave the way for the applications of silicene in spin-valleytronics.

Equal-spin Andreev reflection in antiferromagnet/normal/superconductor junctions with Rashba spin–orbit coupling

“…This phenomenon has also been observed in F/S junctions [14,24] and F/S/ferromagnet double-barrier junctions [17] recently. In particular, Huang [57] reported that conductance peak splitting occurs in a silicene-superconductor junction. In contrast to previous work, Huang focused on the valley degree of freedom rather than the spin degree of freedom and discovered that the conductance peak splitting results from competition between the valley-singlet and valley-triplet states induced in normal silicene.…”

Theoretical valley-polarized subgap transport and intravalley pairing states in a silicene-based antiferromagnet–superconductor junction

“…N Kσ > N K ′ σ , leading to the AF-induced valley polarization in silicene. This differs from the ferromagnetic exchange field or off-resonant light, which generates spin polarization in silicene [39,40]. When an electric field is also applied in the AF region, the spin degeneracy for the K and/or K ′ valleys is lifted, giving rise to the spin polarization in silicene.…”

“…In this paper, we propose a silicene-based AF/homo-or bulk-SC junction to study the valley-polarized subgap transport. The antiferromagnetic exchange field λ AF itself can induce valley polarization in silicene without the aid of an electric field, unlike the ferromagnetic exchange field or light field only generating spin polarization [39,40]. It is shown that, for a large λ AF , the Andreev-resonant peak at gap edge is supplanted by broadened features for the homo-SC model whereas by a sharp conductance dip for the bulk-SC model.…”

“…The zero-bias conductance G(0) at P v = 1 comes from the intravalley AR induced by valley-mixing scattering, which is termed the valley-triplet conductance. Here, the perfect valley-polarized intravalley pairing process can be achieved by the proximity-induced antiferromagnetism without the aid of an electric field, unlike such pairing states in [39][40][41] that require both the external electric field and light field (or ferromagnetic exchange field) in silicene.…”

“…The intravalley AR stems from the valley-mixing scattering at the interface, where the incident electron and reflected hole come from the same valley. Although the intravalley AR process has been studied in silicene/SC junctions [39,40], it needs an external electric field in silicene. In the present structure, the valley-polarized intravalley pairing process including the perfect one can be achieved by the proximity-induced antiferromagnetism without an electric field.…”