Wideband and On-Chip Excitation for Dynamical Spin Injection into Graphene

Indolese, David I.; Zihlmann, Simon; Makk, Péter; Jünger, Christian; Thodkar, Kishan; Schönenberger, Christian

doi:10.1103/physrevapplied.10.044053

Cited by 8 publications

(5 citation statements)

References 50 publications

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“…Future theoretical study should address the parameter dependence such as the dependence of spin current flows on the magnetization direction. The numerical calculation predicted a transverse spin current density 10 −13 J∕m pumped into an InAs 2DEG [83], which is almost 2 orders of magnitude larger than what has been observed for the spin pumping by a Py slab into the graphene [454]. We note that its signal should indeed be much smaller with a small factor.…”

Section: Conservation Of Photon Transverse Spin and Electron Spinmentioning

confidence: 53%

Chirality as Generalized Spin-Orbit Interaction in Spintronics

Chen¹,

Luo²,

Bauer³

2022

Preprint

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Chirality or handedness is a digital relation between three vectors that distinguishes an object from its mirror image, such as the spread fingers of the right and left hand. The chirality of ground state magnetic textures defined by the vectors of magnetization, its gradient, and an electric field from broken inversion symmetry can be fixed by a strong relativistic spin-orbit interaction. This review focuses on the chirality observed in the excited states of the magnetic order, dielectrics, and conductors that hold transverse spins when they are evanescent. Even without any relativistic effect, the transverse spin of the evanescent waves are locked to the momentum and the surface normal of their propagation plane. This chirality thereby acts as a generalized spin-orbit interaction, which leads to the discovery of various chiral interactions between magnetic, phononic, electronic, photonic, and plasmonic excitations in spintronics that mediate the excitation of quasiparticles into a single direction, leading to phenomena such as chiral spin and phonon pumping, chiral spin Seebeck, spin skin, magnonic trap, magnon Doppler, and spin diode effects. Intriguing analogies with electric counterparts in the nano-optics and plasmonics exist. After a brief review of the concepts of chirality that characterize the ground state chiral magnetic textures and chirally coupled magnets in spintronics, we turn to the chiral phenomena of excited states. We present a unified electrodynamic picture for dynamical chirality in spintronics in terms of generalized spin-orbit interaction and compare it with that in nano-optics and plasmonics. Based on the general theory, we subsequently review the theoretical progress and experimental evidence of chiral interaction, as well as the near-field transfer of the transverse spins, between various excitations in magnetic, photonic, electronic and phononic nanostructures at GHz time scales. We provide a perspective for future research before concluding this article.

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Section: Conservation Of Photon Transverse Spin and Electron Spinmentioning

confidence: 53%

Chirality as Generalized Spin-Orbit Interaction in Spintronics

Chen¹,

Luo²,

Bauer³

2022

Preprint

View full text Add to dashboard Cite

show abstract

“…Here we focus on transverse spin pumping into a conductor, which is most efficient for low-dimensional electron systems. We predict here a transverse spin current density 10 −13 J=m pumped into an InAs 2DEG, which is almost 2 orders of magnitude larger than what has been observed for the spin pumping by a Py slab into graphene [29], whose signal should indeed be much smaller with small g factor. We therefore cannot exclude that the observations are caused by dipolar fields at the edge of Py and not exchange interactions at interface.…”

mentioning

confidence: 48%

“…1. The latter may be graphene [27][28][29][30], but the effect is strongly enhanced by spin-orbit interaction, such as a large g factor in InAs or InSb quantum wells (QWs) [31,32] or the surface states of 3D topological insulators [33,34]. In contrast to the dipolar spin pumping of magnons, the spin pumping current in noninteracting conductors is in general not chiral.…”

mentioning

confidence: 99%

Noncontact Spin Pumping by Microwave Evanescent Fields

Bauer

2020

Phys. Rev. Lett.

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The angular momentum of evanescent light fields has been studied in nano-optics and plasmonics but not in the microwave regime. Here we predict noncontact pumping of electron spin currents in conductors by the evanescent stray fields of excited magnetic nanostructures. The coherent transfer of the photon to the electron spin is proportional to the g factor, which is large in narrow gap semiconductors and surface states of topological insulators. The spin pumping current is chiral when the spin susceptibility displays singularities that indicate collective states. However, 1D systems with linear dispersion at the Fermi energy, such as metallic carbon nanotubes, are an exception since spin pumping is chiral even without interactions.

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“…Recent broadband ferromagnetic resonance spectrometer enables the generation of microwaves with frequencies ≤ 40GHz and FMR measurements in a magnetic field ≤ 2T, and the graphene Landau levels are observed in recent experiments at 2T [33]. The modulation of the FMR linewidth in Permalloy/Graphene [15,17], yttrium iron garnet/Graphene [18,19] have been reported by several experimental groups, although all of them were performed at room temperature. Therefore, the above two conditions are experimentally feasible and our theoretical predictions can be tested in an appropriate experimental setup.…”

mentioning

confidence: 99%

“…The proximity exchange coupling describes spin transfer at the magnetic interface and a spin current is injected using ferromagnetic resonance (FMR) from ferromagnetic materials into the adjacent materials. The generation of a spin current is experimentally detectable through both the inverse spin Hall effect and modulation of the FMR, which were experimentally confirmed at magnetic interfaces between graphene and several magnetic materials [15][16][17][18][19].…”

mentioning

confidence: 99%

Quantum Oscillations of Gilbert Damping in Ferromagnetic/Graphene Bilayer Systems

Ominato

Matsuo

2020

J. Phys. Soc. Jpn.

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We study the spin dynamics of a ferromagnetic insulator on which graphene is placed. We show that the Gilbert damping is enhanced by the proximity exchange coupling at the interface. The modulation of the Gilbert damping constant is proportional to the product of the spin-up and spin-down densities of states of graphene. Consequently, the Gilbert damping constant in a strong magnetic field oscillates as a function of the external magnetic field that originates from the Landau level structure of graphene. We find that a measurement of the oscillation period enables the strength of the exchange coupling constant to be determined. The results demonstrate in theory that the ferromagnetic resonance measurements may be used to detect the spin resolved electronic structure of the adjacent materials, which is critically important for future spin device evaluations.Introduction.-The half-integer quantum Hall effect in graphene is a hallmark of two-dimensional Weyl fermions [1,2]. The Landau level structure under a perpendicular magnetic field is notably distinct from conventional twodimensional electron gases in semiconductor quantumwells. In addition to the manifestation of the unusual quantum Hall effect, graphene is a promising material for seeking new phenomena in the quantum Hall regime from the perspectives of the feasibility of the effect and tunability of electronic structures. The quantum Hall effect in graphene is observable even at room temperature [3], and the electronic structure of graphene may be widely modulated by the manner of stacking and the coupling from its substrates. Moiré superlattices arising in graphene on hexagonal boron nitride is a prominent example, for which a fractal energy spectrum under a perpendicular magnetic field called Hofstadters butterfly has been observed [4,5]. The approach using the coupling between graphene and substrates plays a key role for the emergence of new phenomena.

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Wideband and On-Chip Excitation for Dynamical Spin Injection into Graphene

Cited by 8 publications

References 50 publications

Chirality as Generalized Spin-Orbit Interaction in Spintronics

Chirality as Generalized Spin-Orbit Interaction in Spintronics

Noncontact Spin Pumping by Microwave Evanescent Fields

Quantum Oscillations of Gilbert Damping in Ferromagnetic/Graphene Bilayer Systems

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