Electric control of superconducting transition through a spin-orbit coupled interface

Ouassou, Jabir Ali; Bernardo, Angelo Di; Robinson, Jason W. A.; Linder, Jacob

doi:10.1038/srep29312

Cited by 22 publications

(14 citation statements)

References 63 publications

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“…Although not directly comparable, these results show similar behaviour as obtained by a quasiclassical approach in the diffusive limit in Ref. [28,29]. In these works, it was shown that for equal weights of Rashba and Dresselhaus SOC, rotating the magnetic field over an interval of π/2 causes the critical temperature to go from minimum to maximum.…”

Section: Critical Temperaturesupporting

confidence: 85%

Tunable superconducting critical temperature in ballistic hybrid structures with strong spin-orbit coupling

Simensen¹,

Linder²

2018

Phys. Rev. B

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We present a theoretical description and numerical simulations of the superconducting transition in hybrid structures including strong spin-orbit interactions. The spin-orbit coupling is taken to be of Rashba type for concreteness, and we allow for an arbitrary magnitude of the spin-orbit strength as well as an arbitrary thickness of the spin-orbit coupled layer. This allows us to make contact with the experimentally relevant case of enhanced interfacial spin-orbit coupling via atomically thin heavy metal layers. We consider both interfacial spin-orbit coupling induced by inversion asymmetry in an S/F-junction, as well as in-plane spin-orbit coupling in the ferromagnetic region of an S/F/S-and an S/F-structure. Both the pair amplitudes, local density of states and critical temperature show dependency on the Rashba strength and, importantly, the orientation of the exchange field. In general, spin-orbit coupling increases the critical temperature of a proximity system where a magnetic field is present, and enhances the superconducting gap in the density of states. We perform a theoretical derivation which explains these results by the appearance of long-ranged singlet correlations. Our results suggest that T c in ballistic spin-orbit coupled superconducting structures may be tuned by using only a single ferromagnetic layer.

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Section: Critical Temperaturesupporting

confidence: 85%

Tunable superconducting critical temperature in ballistic hybrid structures with strong spin-orbit coupling

Simensen¹,

Linder²

2018

Phys. Rev. B

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“…An interesting expansion of the present work would be to explore how magnetic interfaces232425 and spin-orbit coupling would influence the proximity-gap phase diagram and topological properties of multiterminal Josephson junctions, as recent works have demonstrated that in particular the latter of these can induce several novel effects in both diffusive and ballistic superconducting hybrids13262728293031323334.…”

Section: Resultsmentioning

confidence: 99%

Analytically determined topological phase diagram of the proximity-induced gap in diffusive n-terminal Josephson junctions

Amundsen

Ouassou

Linder

2017

Sci Rep

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Multiterminal Josephson junctions have recently been proposed as a route to artificially mimic topological matter with the distinct advantage that its properties can be controlled via the superconducting phase difference, giving rise to Weyl points in 4-terminal geometries. A key goal is to accurately determine when the system makes a transition from a gapped to non-gapped state as a function of the phase differences in the system, the latter effectively playing the role of quasiparticle momenta in conventional topological matter. We here determine the proximity gap phase diagram of diffusive n-terminal Josephson junctions ( ∈ N n ), both numerically and analytically, by identifying a class of solutions to the Usadel equation at zero energy in the full proximity effect regime. We present an analytical equation which provides the phase diagram for an arbitrary number of terminals n. After briefly demonstrating the validity of the analytical approach in the previously studied 2-and 3-terminal cases, we focus on the 4-terminal case and map out the regimes where the electronic excitations in the system are gapped and non-gapped, respectively, demonstrating also in this case full agreement between the analytical and numerical approach.The interest in topological quantum phases of matter has grown steadily in recent years, and the fundamental importance of this topic in physics was recently recognized by Thouless, Haldane, and Kosterlitz being awarded the 2016 Nobel prize in physics for their contribution to this field. So far, specific material classes such as telluride-based quantum wells (HgTe, CdTe), bismuth antimony (Bi 1−x Sb x ) and bismuth selenide (Bi 2 Se 3 ) have received the most attention in the pursuit of symmetry-protected topological phases and excitations 1-4 . However, it was recently proposed 5 that similar physics could be obtained using conventional superconducting materials. More specifically, by using multiterminal Josephson junctions, the authors of ref. 5 showed that it was possible to create an artificial topological material displaying Weyl singularities under appropriate conditions. In multiterminal Josephson junctions hosting well-defined Andreev bound states, the crossing of these states with the Fermi level has been shown to be analogous to Weyl points in 3D solids with the Andreev bound state taking on the role of energy bands and the superconducting phase differences corresponding to quasiparticle momenta. A considerable advantage in utilizing multiterminal Josephson junctions rather than 3D solids to study exotic phenomena such as Weyl singularities and topologically different phases is that the phase differences are much more easily controlled experimentally than the quasiparticle momenta.In order to probe electronic excitations with topological properties, a key goal is to map out the phase diagram of the system in terms of when it is gapped or not. A gapped system here means that there are no available excitations in a finite interval around the Fermi level. The reason for why this...

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“…This variation is attributed to the generation of triplet Cooper pairs with increasing misalignment of the magnetizations of F1 and F2 layer moments. Recent research [9][10][11][12] has reported a similar modulation of the critical temperature by changing the orientation of a single homogeneous ferromagnet coupled to a superconductor through a thin heavy normal metal (HM) film with strong Rashba spin-orbit coupling. Measurements [12] performed on a Nb/Pt/Co/Pt system showed a suppression of the critical temperature for an in-plane (IP) magnetization that was attributed to a reduced superconducting gap due to triplet generation.…”

Section: Introductionmentioning

confidence: 99%

Magnetization reorientation due to the superconducting transition in heavy-metal heterostructures

2019

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Recent theoretical and experimental work has demonstrated how the superconducting critical temperature (Tc) can be modified by rotating the magnetization of a single homogeneous ferromagnet proximity-coupled to the superconducting layer. This occurs when the superconductor and ferromagnet are separated by a thin heavy normal metal that provides an enhanced interfacial Rashba spin-orbit interaction. In the present work, we consider the reciprocal effect: magnetization reorientation driven by the superconducting phase transition. We solve the tight-binding Bogoliubov-de Gennes equations on a lattice self-consistently and compute the free energy of the system. We find that the relative angle between the spin-orbit field and the magnetization gives rise to a contribution in the free energy even in the normal state, T > Tc, due to band-structure effects. For temperatures below Tc, superconductivity gives rise to a competing contribution. We demonstrate that by lowering the temperature, in addition to reorientation of the favored magnetization direction from in-plane to out-of-plane, a π/4 in-plane rotation for thicker ferromagnetic layers is possible. Furthermore, computation of Tc of the structure in the ballistic limit shows a dependence on the in-plane orientation of the magnetization, in contrast to our previous result on the diffusive limit. This finding is relevant with respect to thin-film heterostructures since these are likely to be in the ballistic regime of transport rather than in the diffusive regime. Finally, we discuss the experimental feasibility of observing the magnetic anisotropy induced by the superconducting transition when other magnetic anisotropies, such as the shape anisotropy for a ferromagnetic film, are taken into account. Our work suggests that the superconducting condensation energy in principle can trigger a reorientation of the magnetization of a thin-film ferromagnet upon lowering the temperature below Tc, in particular for ferromagnets with weak magnetic anisotropies.

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Electric control of superconducting transition through a spin-orbit coupled interface

Cited by 22 publications

References 63 publications

Tunable superconducting critical temperature in ballistic hybrid structures with strong spin-orbit coupling

Tunable superconducting critical temperature in ballistic hybrid structures with strong spin-orbit coupling

Analytically determined topological phase diagram of the proximity-induced gap in diffusive n-terminal Josephson junctions

Magnetization reorientation due to the superconducting transition in heavy-metal heterostructures

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