Conductance spectra of ferromagnetic superconductors: Quantum transport in a ferromagnetic metal/non-unitary ferromagnetic superconductor junction

Linder, Jacob; Gronsleth, M. S.; Sudbø, Asle

doi:10.1103/physrevb.75.054518

Cited by 24 publications

(7 citation statements)

References 40 publications

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“…For simplicity, we will mostly focus on Andreev reflection with ∆ being a spin singlet with orbital s-wave symmetry, referred also as conventional pairing. However, superconducting pairing can also include other orbital symmetries (such as d-wave with nodes in the superconducting gap), spin triplet pairing, and even coexistence with ferromagnetism (Linder et al, 2007). Instead of electron and hole quasiparticles in the normal metals, there are electron-like and hole-like quasiparticles in the superconductor showing predominantly electron or hole character.…”

Section: G1 Conventional Andreev Reflectionmentioning

confidence: 99%

Semiconductor spintronics

Fabian¹,

Matos-Abiague²,

Ertler³

et al. 2007

Acta Physica Slovaca. Reviews and Tutorials

916

1,204

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Spintronics refers commonly to phenomena in which the spin of electrons in a solid state environment plays the determining role. In a more narrow sense spintronics is an emerging research field of electronics: spintronics devices are based on a spin control of electronics, or on an electrical and optical control of spin or magnetism. While metal spintronics has already found its niche in the computer industry-giant magnetoresistance systems are used as hard disk read heads-semiconductor spintronics is yet to demonstrate its full potential. This review presents selected themes of semiconductor spintronics, introducing important concepts in spin transport, spin injection, Silsbee-Johnson spin-charge coupling, and spindependent tunneling, as well as spin relaxation and spin dynamics. The most fundamental spin-dependent interaction in nonmagnetic semiconductors is spin-orbit coupling. Depending on the crystal symmetries of the material, as well as on the structural properties of semiconductor based heterostructures, the spin-orbit coupling takes on different functional forms, giving a nice playground of effective spin-orbit Hamiltonians. The effective Hamiltonians for the most relevant classes of materials and heterostructures are derived here from realistic electronic band structure descriptions. Most semiconductor device systems are still theoretical concepts, waiting for experimental demonstrations. A review of selected proposed, and a few demonstrated devices is presented, with detailed description of two important classes: magnetic resonant tunnel structures and bipolar magnetic diodes and transistors. In view of the importance of ferromagnetic semiconductor materials, a brief discussion of diluted magnetic semiconductors is included. In most cases the presentation is of tutorial style, introducing the essential theoretical formalism at an accessible level, with case-study-like illustrations of actual experimental results, as well as with brief reviews of relevant recent achievements in the field. 72.25.Rb, 75.50.Pp, PACS

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Section: G1 Conventional Andreev Reflectionmentioning

confidence: 99%

Semiconductor spintronics

Fabian¹,

Matos-Abiague²,

Ertler³

et al. 2007

Acta Physica Slovaca. Reviews and Tutorials

916

1,204

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“…where f kk ′ (E) is a diagonal matrix given by equation (31), and ′ is the rate matrix, where ζ kk ′ is the interlayer hopping matrix, and ρ k1k2 (E) is the Fourier transform of equation (25) in the 2D k space. Generally, the hopping matrix is not diagonal, neither is the spectral matrix ρ k1k2 (E) because the QAHI has no translational invariance due to the boundary.…”

Section: Triplet Magnetoresistance Effectmentioning

confidence: 99%

“…Experimentally, the states with broken TRS can be detected by using the muon spin relaxation technique [9]. Theoretical efforts to identify nonunitary states in observables have been focused on the electric conductance of normal-superconductor interfaces [16,[24][25][26] and on finite-energy gap structures in the spectrum of superconductors [13,19]. Generally, signatures of nonunitary states remain elusive if there is no means of controlling the TRS breaking in the superconducting state.…”

Section: Introductionmentioning

confidence: 99%

Nonequilibrium Green’s function approach to multi-band Cooper-pair transport: linear magnetoresistance effect due to nonunitary superconductivity

Tkachov¹

2023

J. Phys.: Condens. Matter

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Many-body transport has emerged as an eﬃcient tool for understanding interaction eﬀects in quantum materials with a multi-band electronic structure. This paper proposes a formula for the two-particle transmission coeﬃcient for Cooper-pair transport between multi-band normal and superconducting materials. The approach employs a tight-binding nonequilibrium Green’s function technique, allowing a direct calculation of the two-particle current, without invoking the paradigm of Andreev reﬂection. As an application of the theory, we demonstrate a low-ﬁeld linear magnetoresistance eﬀect for superconductors with an induced nonunitary order parameter. These results uncover an unexplored route for detecting unconventional nonunitary superconductivity in quantum materials of current theoretical and experimental interest.

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“…Theoretical works in the context of nonunitary superconductivity have explored disorder-induced mixed-parity superconductivity in noncentrosymmetric monolayer transition-metal dichalcogenides [26], and field-induced mixed-parity in locally noncentrosymmetric materials [27]. Experimental observables such as the magnetoelectric Andreev effect [28] and signatures in the conductance spectra in ferromagnetic metal/nonunitary superconductor junctions [29] were proposed. More recently, the opening of gaps away from the Fermi surface in Dirac materials was suggested as a signature of multi-orbital nonunitary superconductivity [30].…”

Section: Introductionmentioning

confidence: 99%

Nonunitary Superconductivity in Complex Quantum Materials

Ramires

2022

Preprint

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We present a comprehensive discussion on nonunitary superconductivity in complex quantum materials. Starting with a brief review of the notion of nonunitary superconductivity, we discuss its spectral signatures in simple models with only the spin as an internal degree of freedom. In complex materials with multiple internal degrees of freedom, there are many more possibilities for the development of nonunitary order parameters. We provide examples focusing on d-electron systems with two orbitals, applicable to a variety of materials. We discuss the consequences for the superconducting spectra, highlighting that gap openings of band crossings at finite energies can be attributed to a nonunitary order parameter if this is associated with a finite superconducting fitness matrix FC (k). We speculate that nonunitary superconductivity in complex quantum materials is in fact very common and can be associated with multiple cases of time-reversal symmetry breaking superconductors.

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Conductance spectra of ferromagnetic superconductors: Quantum transport in a ferromagnetic metal/non-unitary ferromagnetic superconductor junction

Cited by 24 publications

References 40 publications

Semiconductor spintronics

Semiconductor spintronics

Nonequilibrium Green’s function approach to multi-band Cooper-pair transport: linear magnetoresistance effect due to nonunitary superconductivity

Nonunitary Superconductivity in Complex Quantum Materials

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