Equal-spin Andreev reflection in ferromagnet/superconductor junctions with the interfacial Rashba spin-orbit coupling

Niu, Zhi Ping

doi:10.1209/0295-5075/100/17012

Cited by 18 publications

(17 citation statements)

References 58 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A somewhat similar example that has been extensively discussed in the literature is that of half metal-superconductor bilayers with spin-flip interface. 32,33,60,61 There the spin-flip interface plays the same role as the weaker ferromagnet here. Another interesting phenomenon also related to ESAR is the induction of triplet pairing correlations in F-S structures.…”

Section: Anomalous Andreev Reflectionmentioning

confidence: 76%

“…30 The pairing state of m = ±1 induced triplet correlations is at variance with the effects of conventional Andreev reflection, responsible for the generation of singlet Cooper pairs. Thus, recent studies [31][32][33][34][35] on the tunneling conductance propose the existence of anomalous Andreev reflection, that is, a reflected hole with the same spin as the incident particle can be Andreev reflected under the same circumstances as the generation of m = ±1 triplet pairing correlations becomes possible. In this view, triplet proximity effects are correlated with the process of this anomalous Andreev reflection.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Tunneling conductance and spin transport in clean ferromagnet/ferromagnet/superconductor heterostructures

Valls

Halterman

2014

Phys. Rev. B

View full text Add to dashboard Cite

We present a transfer matrix approach that combines the Blonder-Tinkham-Klapwijk (BTK) formalism and self-consistent solutions to the Bogolibuov-de Gennes (BdG) equations and use it to study the tunneling conductance and spin transport in ferromagnet (F)-superconductor (S) trilayers (F 1 F 2 S) as functions of bias voltage. The self-consistency ensures that the spin and charge conservation laws are properly satisfied. We consider forward and angularly averaged conductances over a broad range of the strength of the exchange fields and F thicknesses, as the relative in-plane magnetization angle, φ, between the two ferromagnets varies. The φdependence of the self-consistent conductance curves in the trilayers can differ substantially from that obtained via a non-self-consistent approach. The zero bias forward conductance peak exhibits, as φ varies, resonance effects intricately associated with particular combinations of the geometrical and material parameters. We find, when the magnetizations are non-collinear, signatures of the anomalous Andreev reflections in the subgap regions of the angularly averaged conductances. When F 1 is half-metallic, the angularly averaged subgap conductance chiefly arises from anomalous Andreev reflection. The in-plane components of the spin current are strongly bias dependent, while the out-of-plane spin current component is only weakly dependent upon voltage. The components of the spin current aligned with the local exchange field of one of the F layers are conserved in that layer and in the S region, while they oscillate in the other layer. We compute the spin transfer torques, in connection with the oscillatory behavior of spin currents, and verify that the spin continuity equation is strictly obeyed in our method.

show abstract

Section: Anomalous Andreev Reflectionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Tunneling conductance and spin transport in clean ferromagnet/ferromagnet/superconductor heterostructures

Valls

Halterman

2014

Phys. Rev. B

View full text Add to dashboard Cite

show abstract

“…Pure equal spin Andreev reflections can take place at a half-metal/superconductor interface [21][22][23][24][25][26][27][28] if spin is not conserved at the interface. This is because conducting electrons in a half-metal are fully spin-polarized and usual Andreev reflection processes cannot occur.…”

mentioning

confidence: 99%

Selective Equal-Spin Andreev Reflections Induced by Majorana Fermions

et al. 2014

View full text Add to dashboard Cite

In this work, we find that Majorana fermions induce selective equal spin Andreev reflections (SESARs), in which incoming electrons with certain spin polarization in the lead are reflected as counter-propagating holes with the same spin. The spin polarization direction of the electrons of this Andreev reflected channel is selected by the Majorana fermions. Moreover, electrons with opposite spin polarization are always reflected as electrons with unchanged spin. As a result, the charge current in the lead is spin-polarized. Therefore, a topological superconductor which supports Majorana fermions can be used as a novel device to create fully spin-polarized currents in paramagnetic leads. We point out that SESARs can also be used to detect Majorana fermions in topological superconductors. [18,19]. Introduction-In this work, we point out another intriguing phenomenon due to the self-Hermitian property of MFs, namely, MF-induced selective equal spin Andreev reflections (SESARs). As depicted in Fig.1, when a spinful paramagnetic normal lead is coupled to a topological superconductor through its MF end state, electrons with spin pointing to a certain direction n are reflected as holes with the same spin (Fig.1a), where n is determined by the properties of the topological superconductor. The reflected holes are created due to missing electrons with spin polarization n below the Fermi energy. Therefore, these processes are called equal spin Andreev reflections. This is in sharp contrast to ordinary Andreev reflection processes [20], in which the reflected holes are created due to missing electrons below the Fermi energy which have opposite spins to the incoming electrons.Even more interestingly, at the normal lead/topological superconductor (N/TS) junction, electrons with opposite spin polarization − n are completely decoupled from the MF and they cannot participate in Andreev reflections (Fig.1b). In other words, the MF selects electrons with certain spin polarization n to undergo equal spin Andreev reflections. Therefore, we refer to this new phenomenon as MF-induced SESARs.Pure equal spin Andreev reflections can take place at a half-metal/superconductor interface [21-28] if spin is not conserved at the interface. This is because conducting electrons in a half-metal are fully spin-polarized and usual Andreev reflection processes cannot occur. Nevertheless, as we show below, inducing SESARs in paramagnetic leads is a special property of MFs. Importantly, as in the half-metal case and depicted in Fig.1a, the charge

show abstract

“…For instance, near the interface, an electron with a certain spin injected from N is retro-reflected as a hole of the opposite spin via a conventional local Andreev reflection (LAR). In situations where the spin flip is allowed at the interface, equal-spin AR can occur, where both the electron and the hole have the same spin [4,5]. Recently, it has been shown that equal-spin AR can also be induced by the Majorana bound state (MBS) residing on the edge of a semi-infinite topological superconducting nanowire with spin-orbit coupling (SOC), Zeeman splitting and proximity-induced superconductivity [6,7].…”

mentioning

confidence: 99%

Noncollinear Andreev reflections in semiconductor nanowires

Cao

et al. 2014

Phys. Rev. B

View full text Add to dashboard Cite

We show that noncollinear Andreev reflections can be induced at interfaces of semiconductor nanowires with spin-orbit coupling, Zeeman splitting and proximity-induced superconductivity. In a noncollinear local Andreev reflection, the spin polarizations of the injected and the retro-reflected carriers are typically at an angle which is tunable via system parameters. While in a nonlocal transport, this noncollinearity enables us to identify and block, at different voltage configurations, the noncollinear cross Andreev reflection and the direct charge transfer processes. We demonstrate that the intriguing noncollinearity originates from the spin-dependent coupling between carriers in the lead and the lowest discrete states in the wire, which, for a topological superconducting nanowire, are related to the overlap-induced hybridization of Majorana edge states in a finite system. These interesting phenomena can be observed in semiconductor nanowires of experimentally relevant lengths, and are potentially useful for spintronics.

show abstract

Equal-spin Andreev reflection in ferromagnet/superconductor junctions with the interfacial Rashba spin-orbit coupling

Cited by 18 publications

References 58 publications

Tunneling conductance and spin transport in clean ferromagnet/ferromagnet/superconductor heterostructures

Tunneling conductance and spin transport in clean ferromagnet/ferromagnet/superconductor heterostructures

Selective Equal-Spin Andreev Reflections Induced by Majorana Fermions

Noncollinear Andreev reflections in semiconductor nanowires

Contact Info

Product

Resources

About