Spin-Controlled Superconductivity and Tunable Triplet Correlations in Graphene Nanostructures

Halterman, Klaus; Valls, Oriol T.; Alidoust, Mohammad

doi:10.1103/physrevlett.111.046602

Cited by 51 publications

(55 citation statements)

References 38 publications

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“…Accordingly, the splitting of the ZBCP first strengthens and then weakens. Hence, the equal-spin triplet pairing states in this graphene-based d-wave SC junction are also controllable by tuning the Fermi levels, which is consistent with those of [30,31].…”

Section: Influence Of Tunable Chemical Potentialsupporting

confidence: 74%

“…This novel equal-spin AR results in nonvanishing superconducting triplet equal-spin pairings in the ferromagnetic region near the FM/RSO interface [30]. In most previous theoretical works on the spin-triplet pairing in graphene-based FM/ SC structures, the SC layer was assumed to be of s-wave [30][31][32]. However, the spin-triplet AR in the graphenebased d-wave SC junctions has not been studied so far.…”

Section: Introductionmentioning

confidence: 99%

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Identifying the graphene d-wave superconducting symmetry by an anomalous splitting zero-bias conductance peak

et al. 2020

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Not until recently, was a gate-tunable, high-temperature superconducting proximity effect in graphene demonstrated experimentally. And usually in d-wave superconductor (SC) hybrid structure, ferromagnetism and spin-triplet states could result in a splitting zero-bias conductance peak (ZBCP). Herein, we theoretically present an anomalous splitting ZBCP in a graphene-based ferromagnet/ Rashba spin-orbit coupling (RSOC)/insulator/d-wave SC hybrid structure. With increasing the exchange field from h/E F =0, the ZBCP starts to turn into a splitting one with a zero-bias conductance dip (ZBCD) sandwiched in between two subpeaks, while from h/E F =1, the two subpeaks and ZBCD begin to gradually shrink till the ZBCP reappears. The anomalous splitting ZBCP can be modulated by the RSOC strength, magnitude of Fermi wave vector mismatch as well as insulator barrier strength. These peculiar features are ascribed to the novel spin-triplet Andreev reflection in the context of the RSOC, characteristic by the anisotropic d-wave pair symmetry combined with the relativistic nodal fermions, which in turn can be experimentally used to directly identify not only the proximity-induced ferromagnetism and RSOC but d-wave pair symmetry in graphene. These results pave the way to a new class of tunable, high-temperature superconducting spintronic devices based on large-scale graphene.

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Section: Influence Of Tunable Chemical Potentialsupporting

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Identifying the graphene d-wave superconducting symmetry by an anomalous splitting zero-bias conductance peak

et al. 2020

View full text Add to dashboard Cite

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“…On the other hand, the interplay of s-wave superconductivity and an inhomogeneous magnetization can convert the superconducting spin singlet correlations into equal spin triplets [29,30]. After the theoretical predic-tion of the spin triplet superconducting correlations much effort has been made to confirm their existence [4,[31][32][33][34][35][36][37][38][39][40][41][42][43][44]. For example, a finite supercurrent was observed in a halfmetallic junction that was attributed to the generation of equal spin triplet correlations near the superconductorhalf metal interface [31].…”

mentioning

confidence: 99%

“…57-59 for isolated samples. Therefore, the low energy behaviour of quasiparticles, quantum transport characteristics, and thermodynamics of such a system can be described by the Dirac Bogoliubov-de Gennes (DBdG) formalism [35,60]:…”

mentioning

confidence: 99%

Nonlocal Andreev entanglements and triplet correlations in graphene with spin-orbit coupling

2017

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Using a wavefunction Dirac Bogoliubov-de Gennes method, we demonstrate that the tunable Fermi level of a graphene layer in the presence of Rashba spin orbit coupling (RSOC) allows for producing an anomalous nonlocal Andreev reflection and equal spin superconducting triplet pairing. We consider a graphene junction of a ferromagnet-RSOC-superconductor-ferromagnet configuration and study scattering processes, the appearance of spin triplet correlations, and charge conductance in this structure. We show that the anomalous crossed Andreev reflection is linked to the equal spin triplet pairing. Moreover, by calculating current cross-correlations, our results reveal that this phenomenon causes negative charge conductance at weak voltages and can be revealed in a spectroscopy experiment, and may provide a tool for detecting the entanglement of the equal spin superconducting pair correlations in hybrid structures. PACS numbers: 72.80.Vp, 74.45.+c, 74.50.+r, 81.05.ue Introduction-Superconductivity and its hybrid structures with other phases can host a wide variety of intriguing fundamental phenomena and functional applications such as Higgs mechanism [1], Majorana fermions [2], topological quantum computation [3], spintronics [4], and quantum entanglement [5][6][7][8]. The quantum entanglement describes quantum states of correlated objects with nonzero distances [6,8] that are expected to be employed in novel ultra-fast technologies such as secure quantum computing [3,6].

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“…The low-energy excitation in F segment is described by the Dirac-type equation, H F = (s z ⊗ σ 0 ) h in which h refers to the strength of the magnetic exchange field which added to the Dirac Hamiltonian via the Stoner approach. For simplicity, we assume that in both ferromagnetic regions, the magnetic exchange field is oriented in the z-direction, without loss of generality [51]. In the above equations, k x and k y are the components of wave vector in the x and y directions, respectively.…”

Section: Model and Analysismentioning

confidence: 99%

Tunable magnetoresistance in spin-orbit coupled graphene junctions

Beiranvand

Hamzehpour

2019

Journal of Magnetism and Magnetic Materials

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Using the Landauer-Bütikker formalism, we study the graphene magneto-transport in the presence of Rashba spin-orbit interaction (RSOI). we show that the angle resolved transmission probability in the proposed structures can be tuned by the RSOI strength. The transmission spectrum show Klein tunneling in the parallel (P) magnetization configuration which can be blocked by the RSOI. This effect is also observable for the anti-parallel (AP) magnetization configuration in different incident angle. The numerical results shows that the spin-polarized conductance strongly depends on the strength of the RSOI and can be generated by tuning the magnetic exchange field and RSOI strength. This spin-polarized conductance is a sensitive oscillatory function of the thickness of the RSO region. Because of the spin-flip effect, the junction shows a spin-valve effect with large and negative magnetoresistance (MR) and spin-magnetoresistance (SMR) in the presence of RSOI. When the RSOI is on, the frequency and amplitude of shot-noise and Fano factor's oscillations are also increased. These results can provide a way to extending the application of graphene-based junctions in spintronics. * razieh.beiranvand@abru.ac.ir arXiv:1808.03957v1 [cond-mat.mes-hall]

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Spin-Controlled Superconductivity and Tunable Triplet Correlations in Graphene Nanostructures

Cited by 51 publications

References 38 publications

Identifying the graphene d-wave superconducting symmetry by an anomalous splitting zero-bias conductance peak

Identifying the graphene d-wave superconducting symmetry by an anomalous splitting zero-bias conductance peak

Nonlocal Andreev entanglements and triplet correlations in graphene with spin-orbit coupling

Tunable magnetoresistance in spin-orbit coupled graphene junctions

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