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

Abstract

We have theoretically investigated the Andreev reflection induced
conductance spectra through antiferromagnet/normal layer/superconductor
junctions with hexagonal lattices. When the PT symmetry is broken by the staggered sublattice potential, antiferromagnet may exhibit spin polarization. Equal-spin Andreev reflection can be generated by the
spin-flip scattering caused by Rashba spin-orbit coupling in the
normal layer. A gap-edge conductance peak is usually shown, reflecting the characteristic of conventional Andreev reflection. Surprisingly, when the equal-spin Andreev reflection process dominates, the conductance peak divides into two peaks near the singlet-gap energy, indicating the existence of spin-triplet pairings in the antiferromagnet. Furthermore, as the amplitudes of the
conventional and equal-spin Andreev reflections can be modulated 
by the staggered sublattice potential and electrostatic potential,
a conversion from the conductance peak to the conductance peak
splitting can be realized, which can help us 
to distinguish between the spin-singlet and 
spin-triplet pairings. These findings make the
antiferromagnet/superconductor junctions as promising platforms for
future superconducting spintronics applications.

Orientation-dependent Andreev reflection in an altermagnet/altermagnet/superconductor junction

“…∑ r L(R) represents the self-energy due to the coupling between the central AM and the AM (S) lead, which can be calculated numerically [42,43]. The detailed procedure for determining the self-energy can also be found in [39,44]. The linewidth function for the left (right) lead is…”

“…Consider an electron with energy E incident from the left AM. The conductance calculated by the non-equilibrium Green's function method is expressed as [27,39]…”

“…represents the equal-spin AR coefficient [27,39]. Equal-spin AR arises in the presence of spin-flip scattering, where the incident electron and the Andreev-reflected hole stem from the same spin band, forming a spin-triplet pairing with parallel spins.…”

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

“…The formation of low-energy bound states by these scattering processes in Josephson junctions leads to anomalous phase shifts and atomic-scale 0-π transitions [11,12,16]. Moreover, Niu and Zhang [17] have theoretically studied the conductance spectra of a graphenebased AF/Rashba spin-orbit coupling (RSOC)/SC junction, which were predominated by the (equal-spin) spin-triplet AR process. These findings indicate that AF/SC junctions become a promising platform for future superconducting spintronic applications.…”