Excitation of coupled spin–orbit dynamics in cobalt oxide by femtosecond laser pulses

Satoh, Takuya; Iida, Ryugo; Higuchi, Tohru; Fujii, Yasuhiro; Koreeda, Akitoshi; Ueda, Hiroaki; Shimura, Tsutomu; Kuroda, Kazuyuki; Butrim, V. I.; Иванов, Б. А.

doi:10.1038/s41467-017-00616-2

Cited by 46 publications

(50 citation statements)

References 33 publications

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“…[44][45][46][47][48]55 We note that magneto-optical coupling of light and spins is frequently used for exciting ultrafast spin dynamics in antiferromagnetic insulators. [29][30][31] However, we found this mechanism to be irrelevant for generating spin photocurrents. 60 We also demonstrated that in the presence of asymmetric Dzyaloshinskii-Moriya interactions it is possible to induce spin photocurrents using linearly polarized light.…”

Section: Discussionmentioning

confidence: 73%

“…[22][23][24][25] Additionally, a magnonic spin Nernst effect was proposed for quasi-two-dimensional hexagonal antiferromagnets with Dzyaloshinskii-Moriya interactions (DMI) 26,27 and found later experimentally in MnPS 3 . 28 Ultrafast optical excitation of coherent magnon dynamics [29][30][31] is another prominent area, which is in the basic concept of antiferromagnetic optospintronics -a direction targeting optical control of spin states in antiferromagnetic insulators. 32 Although an additional antiferromagnetic layer in a ferromagnet/normal metal interface can sufficiently enhance efficiency of spin pumping, 20,33 and dynamic antiferromagnets can themselves serve as sources of spin currents experiencing a spin backflow from adjacent metal slabs, 34 nonthermal generation of magnon spin currents in bulk antiferromagnets is challenging due to vanishing net magnetic moment.…”

Section: Introductionmentioning

confidence: 99%

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Excitation of magnon spin photocurrents in antiferromagnetic insulators

et al. 2018

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In the circular photogalvanic effect, circularly polarized light can produce a direct electron photocurrent in metals and the direction of the current depends on the polarization. We suggest that an analogous nonlinear effect exists for antiferromagnetic insulators wherein the total spin of light and spin waves is conserved. In consequence, a spin angular momentum is expected to be transfered from photons to magnons so that a circularly polarized electromagnetic field will generate a direct magnon spin current. The direction of the current is determined by the helicity of the light. We show that this resonant effect appears as a second order light-matter interaction. We find also a geometric contribution to the spin photocurrent, which appears for materials with complex lattice structures and Dzyaloshinskii-Moriya interactions.

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Section: Discussionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Excitation of magnon spin photocurrents in antiferromagnetic insulators

et al. 2018

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“…In the monochromatic field limit, the fields in Eqs. (7) and (8) and the resulting Poynting vector can be approximated further as explained in Appendix B. This approximation allows us to perform the integrations in Eqs.…”

Section: B Linear Polarizationmentioning

confidence: 99%

“…After this, the integrals over k in Eqs. (7) and (8) can be evaluated analytically leading to the fields given by E p,l (r, t) ≈ Re iω 0 u p,lx + i∂u p,l nk 0 ∂xẑ e i(nk0z−ω0t)…”

Section: Linear Polarizationmentioning

confidence: 99%

Mass-polariton theory of sharing the total angular momentum of light between the field and matter

Partanen

Tulkki

2018

Phys. Rev. A

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Light propagating in a nondispersive medium is accompanied by a mass density wave (MDW) of atoms set in motion by the optical force of the field itself [Phys. Rev. A 95, 063850 (2017)]. This recent result is in strong contrast with the approximation of fixed atoms, which assumes that atoms are fixed to their equilibrium positions when light propagates in a medium and which is deeply rooted in the conventional electrodynamics of continuous media. In many photonic materials, the atoms carry the majority of the total momentum of light and their motion also gives rise to net transfer of medium mass with a light pulse. In this work, we use optoelastic continuum dynamics combining the optical force field, elasticity theory, and Newtonian mechanics to analyze the angular momentum carried by the MDW. Our calculations are based on classical physics, but by dividing the numerically calculated angular momenta of Laguerre-Gaussian (LG) pulses with the photon number, we can also study the single-quantum values. We show that accounting for the MDW in the analysis of the angular momentum gives for the field's share of the total angular momentum of light a quantized value that is generally a fraction of . In contrast, the total angular momentum of the mass-polariton (MP) quasiparticle, which is a coupled state of the field and the MDW, and also the elementary quantum of light in a medium, is an integer multiple of . Thus, the angular momentum of the MP has coupled field and medium components, which cannot be separately experimentally measured. This discovery is related to the previous observation that a bare photon including only the field part cannot propagate in a medium. The same coupling is found for orbital and spin angular momentum components. The physical picture of the angular momentum of light emerging from our theory is fundamentally more general than earlier theoretical models, in which the total angular momentum of light is assumed to be carried by the electromagnetic field only or by an electronic polariton state, which also involves dipolar electronic oscillations. These models cannot describe the MDW shift of atoms associated with light. We simulate the MDW of LG pulses in silicon and present a schematic experimental setup for measuring the contribution of the atomic MDW to the total angular momentum of light.

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“…A key difference between MnF 2 and both α-CoV 3 O 8 and FeF 2 is the presence of strong crystal field effects and spin-orbit coupling in the latter two compounds 133,175 . It is also worth noting that unlike the case of pure CoO 81,91,94,[181][182][183][184] where the large and far reaching exchange constants result in a significant and ultimately problematic entanglement of spin-orbit levels 94 , in the case of α-CoV 3 O 8 , the exchange constants are weak and the Weiss temperature is near 0 K. Both observations suggest that the presence of both strong crystal field effects and spin-orbit coupling with well-separated j eff manifolds, as is the case for α-CoV 3 O 8 , may be central to making the dynamics robust against strong disorder.…”

Section: Comparison Between α-Cov3o8 and Randommentioning

confidence: 99%

Ordered magnetism in the intrinsically decorated jeff=12α−CoV3O8

et al. 2018

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The antiferromagnetic mixed valence ternary oxide α-CoV3O8 displays disorder on the Co 2+ site that is inherent to the Ibam space group resulting in a local selection rule requiring one Co 2+ and one V 4+ reside next to each other, thus giving rise to an intrinsically disordered magnet without the need for any external influences such as chemical dopants or porous media. The zero field structural and dynamic properties of α-CoV3O8 have been investigated using a combination of neutron and x-ray diffraction, DC susceptibility, and neutron spectroscopy. The low temperature magnetic and structural properties are consistent with a random macroscopic distribution of Co 2+ over the 16k metal sites. However, by applying the sum rules of neutron scattering we observe the collective magnetic excitations are parameterized with an ordered Co 2+ arrangement and critical scattering consistent with a three dimensional Ising universality class. The low energy spectrum is well-described by Co 2+ cations coupled via a three dimensional network composed of competing ferromagnetic and stronger antiferromagnetic superexchange within the ab plane and along c, respectively. While the extrapolated Weiss temperature is near zero, the 3D dimensionality results in long range antiferromagnetic order at T N ∼ 19 K. A crystal field analysis finds two bands of excitations separated in energy at ω ∼ 5 meV and 25 meV, consistent with a j eff = 1 2 ground state with little mixing between spin-orbit split Kramers doublets. A comparison of our results to the random 3D Ising magnets and other compounds where spin-orbit coupling is present indicate that the presence of an orbital degree of freedom, in combination with strong crystal field effects and well-separated j eff manifolds may play a key role in making the dynamics largely insensitive to disorder.

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Excitation of coupled spin–orbit dynamics in cobalt oxide by femtosecond laser pulses

Cited by 46 publications

References 33 publications

Excitation of magnon spin photocurrents in antiferromagnetic insulators

Excitation of magnon spin photocurrents in antiferromagnetic insulators

Mass-polariton theory of sharing the total angular momentum of light between the field and matter

Ordered magnetism in the intrinsically decorated jeff=12α−CoV3O8

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