Superconductivity at metal-antiferromagnetic insulator interfaces

Fjærbu, Eirik Løhaugen; Rohling, Niklas; Brataas, Arne

doi:10.1103/physrevb.100.125432

Cited by 35 publications

(49 citation statements)

References 35 publications

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“…The processes where the momentum of the outgoing electron is shifted by a reciprocal lattice vector G are Umklapp processes. These processes are expected to be important for inducing superconductivity mediated by antiferromagnetic magnons in normal metals at half-filling [15]. For a tight-binding model, on a square lattice, at half-filling, G connects different points on the Fermi surface.…”

Section: And Fourier Transformations Of the Magnon Operators Amentioning

confidence: 99%

Magnon-mediated superconductivity on the surface of a topological insulator

2020

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We study superconductivity on the surface of a topological insulator, mediated by magnetic fluctuations in an adjacent ferromagnetic or antiferromagnetic insulator. Superconductivity can arise from effective interactions between helical fermions induced by interfacial fermion-magnon interactions. For both ferromagnetic and antiferromagnetic insulators, these fermion-fermion interactions have the correct structure to facilitate pairing between particles located on the same side of the Fermi surface, also known as Amperean pairing. In antiferromagnets, the strength of the induced interactions can be enhanced by coupling the topological insulator asymmetrically to the two sublattices of the antiferromagnet. This effect is further amplified by next nearest neighbor frustration in the antiferromagnetic insulator. The enhancement makes the induced interactions significantly stronger in the antiferromagnetic case, as compared to the ferromagnetic case. These results indicate that an uncompensated antiferromagnetic interface might be a better candidate than a ferromagnetic interface for proximity-induced magnon-mediated superconductivity on the surface of a topological insulator. arXiv:1912.07607v2 [cond-mat.supr-con]

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Section: And Fourier Transformations Of the Magnon Operators Amentioning

confidence: 99%

Magnon-mediated superconductivity on the surface of a topological insulator

2020

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“…These excitations are quasiparticles known as magnons. Theoretical predictions of electron-magnon interactions have shown that these can also induce effects such as superconductivity [1][2][3][4][5][6][7][8][9][10].Research interest in antiferromagnetic materials is surging [11,12]. This enthusiasm is due to the promising properties of antiferromagnets such as high resonance frequencies in the THz regime and a vanishing net magnetic moment.…”

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“…Much of this research focuses on interactions involving magnons or spin waves at magnetic interfaces in hybrid structures. Examples of this are spin pumping [13][14][15][16][17][18][19], spin transfer [15,[20][21][22], and spin Hall magnetoresistance [23][24][25][26][27][28] at normal metal interfaces, and magnon-mediated superconductivity [9,10]. Recently, an experiment has also demonstrated spin transport in an antiferromagnetic insulator over distances up to 80 µm [29].…”

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Magnon-Mediated Indirect Exciton Condensation through Antiferromagnetic Insulators

et al. 2019

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Electrons and holes residing on the opposing sides of an insulating barrier and experiencing an attractive Coulomb interaction can spontaneously form a coherent state known as an indirect exciton condensate. We study a trilayer system where the barrier is an antiferromagnetic insulator. The electrons and holes here additionally interact via interfacial coupling to the antiferromagnetic magnons. We show that by employing magnetically uncompensated interfaces, we can design the magnon-mediated interaction to be attractive or repulsive by varying the thickness of the antiferromagnetic insulator by a single atomic layer. We derive an analytical expression for the critical temperature T c of the indirect exciton condensation. Within our model, anisotropy is found to be crucial for achieving a finite T c , which increases with the strength of the exchange interaction in the antiferromagnetic bulk. For realistic material parameters, we estimate T c to be around 7 K, the same order of magnitude as the current experimentally achievable exciton condensation where the attraction is solely due to the Coulomb interaction. The magnon-mediated interaction is expected to cooperate with the Coulomb interaction for condensation of indirect excitons, thereby providing a means to significantly increase the exciton condensation temperature range.Introduction.-Interactions between fermions result in exotic states of matter. Superconductivity is a prime example, where the negatively charged electrons can have an overall attractive coupling mediated by individual couplings to the vibrations, known as phonons, of the positively charged lattice. In addition to charge, the electron also has a spin degree of freedom. The electron spin can interact with localized magnetic moments through an exchange interaction exciting the magnetic moment by transfer of angular momentum. These excitations are quasiparticles known as magnons. Theoretical predictions of electron-magnon interactions have shown that these can also induce effects such as superconductivity [1][2][3][4][5][6][7][8][9][10].Research interest in antiferromagnetic materials is surging [11,12]. This enthusiasm is due to the promising properties of antiferromagnets such as high resonance frequencies in the THz regime and a vanishing net magnetic moment. Much of this research focuses on interactions involving magnons or spin waves at magnetic interfaces in hybrid structures. Examples of this are spin pumping [13-19], spin transfer [15, 20-22], and spin Hall magnetoresistance [23-28] at normal metal interfaces, and magnon-mediated superconductivity [9,10]. Recently, an experiment has also demonstrated spin transport in an antiferromagnetic insulator over distances up to 80 µm [29]. Moreover, antiferromagnetic materials are also of interest since it is believed that high-temperature superconductivity in cuprates is intricately linked to magnetic fluctuations near an antiferromagnetic Mott insulating phase [30,31]. Thus it is crucial to achieve a good understanding of antiferromagnetic magn...

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“…Recent studies have investigated whether spin fluctuations in a magnetic material can induce attractive interactions between electrons in an adjacent conductor, leading to a superconducting instability [1][2][3][4][5][6][7][8]. Both ferromagnetic (FMIs) and antiferromagnetic insulators (AFMIs) have been considered as potential sources for the magnetic fluctuations.…”

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Schwinger boson study of superconductivity mediated by antiferromagnetic spin fluctuations

Erlandsen

Sudbø

2020

Phys. Rev. B

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We study superconductivity in a normal metal, arising from effective electron-electron interactions mediated by spin fluctuations in a neighboring antiferromagnetic insulator. Introducing a frustrating next-nearest neighbor interaction in a Néel antiferromagnet with an uncompensated interface, the superconducting critical temperature is found to be enhanced as the frustration is increased. Further, for sufficiently large next-nearest neighbor interaction, the antiferromagnet is driven into a stripe phase, which can also give rise to attractive electronelectron interactions. For the stripe phase, as previously reported for the Néel phase, the superconducting critical temperature is found to be amplified for an uncompensated interface where the normal metal conduction electrons are coupled to only one of the two sublattices of the magnet. The superconducting critical temperature arising from fluctuations in the stripe phase antiferromagnet can be further enhanced by approaching the transition back to the Néel phase.

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Superconductivity at metal-antiferromagnetic insulator interfaces

Cited by 35 publications

References 35 publications

Magnon-mediated superconductivity on the surface of a topological insulator

Magnon-mediated superconductivity on the surface of a topological insulator

Magnon-Mediated Indirect Exciton Condensation through Antiferromagnetic Insulators

Schwinger boson study of superconductivity mediated by antiferromagnetic spin fluctuations

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