Electron-spin dynamics induced by photon spins

Bauke, Heiko; Ahrens, Sven; Keitel, Christoph H.; Grobe, R.

doi:10.1088/1367-2630/16/10/103028

Cited by 27 publications

(41 citation statements)

References 41 publications

(87 reference statements)

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“…It is therefore customary to describe the spin of a relativistic particle in its rest frame, where we can apply the nonrelativistic theory [52], see also Refs. [57][58][59] a general discussion and for alternative approaches. The components of neither the non-relativisitic or relativisitic spin operators mutually commute, [σ i , σ j ] = 2i ijk σ k .…”

Section: B Description Of the Spin Of Volkov Electronsmentioning

confidence: 99%

Theory of radiative electron polarization in strong laser fields

Seipt¹,

Sorbo²,

Ridgers³

et al. 2018

Phys. Rev. A

114

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Radiative polarization of electrons and positrons through the Sokolov-Ternov effect is important for applications in high-energy physics. Radiative spin polarization is a manifestation of quantum radiation reaction affecting the spin dynamics of electrons. We recently proposed that an analog of the Sokolov-Ternov effect could occur in the strong electromagnetic fields of ultra-high-intensity lasers, which would result in a buildup of spin polarization in femtoseconds. In this paper, we develop a density matrix formalism for describing beam polarization in strong electromagnetic fields. We start by using the density matrix formalism to study spin flips in nonlinear Compton scattering and its dependence on the initial polarization state of the electrons. Numerical calculations show a radial polarization of the scattered electron beam in a circularly polarized laser, and we find azimuthal asymmetries in the polarization patterns for ultrashort laser pulses. A degree of polarization approaching 9% is achieved after emitting just a single photon. We develop the theory by deriving a local constant crossed-field approximation (LCFA) for the polarization density matrix, which is a generalization of the well-known LCFA scattering rates. We find spin-dependent expressions that may be included in electromagnetic charged-particle simulation codes, such as particle-in-cell plasma simulation codes, using Monte Carlo modules. In particular, these expressions include the spin-flip rates for arbitrary initial polarization of the electrons. The validity of the LCFA is confirmed by explicit comparison with an exact QED calculation of electron polarization in an ultrashort laser pulse.

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Section: B Description Of the Spin Of Volkov Electronsmentioning

confidence: 99%

Theory of radiative electron polarization in strong laser fields

Seipt¹,

Sorbo²,

Ridgers³

et al. 2018

Phys. Rev. A

114

View full text Add to dashboard Cite

show abstract

“…(11) is related to the angular momentum of the electromagnetic field and thus provides a torque on the spin that has been at the heart of angular magneto-electric coupling [53]. A possible effect in spin dynamics including the light's angular momentum has been investigated in the strong field regime and it has been shown that one has to include this cross term in the dynamics in order to explain the qualitative and quantitative strong field dynamics [57]. For the last term in the spin Hamiltonian (11) it is rather easy to formulate the spin dynamics because it is evidently hermitian.…”

Section: Magnetization Dynamicsmentioning

confidence: 99%

Relativistic theory of magnetic inertia in ultrafast spin dynamics

et al. 2017

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The influence of possible magnetic inertia effects has recently drawn attention in ultrafast magnetization dynamics and switching. Here we derive rigorously a description of inertia in the Landau-Lifshitz-Gilbert equation on the basis of the Dirac-Kohn-Sham framework. Using the FoldyWouthuysen transformation up to the order of 1/c 4 gives the intrinsic inertia of a pure system through the 2 nd order time-derivative of magnetization in the dynamical equation of motion. Thus, the inertial damping I is a higher order spin-orbit coupling effect, ∼ 1/c 4 , as compared to the Gilbert damping Γ that is of order 1/c 2 . Inertia is therefore expected to play a role only on ultrashort timescales (sub-picoseconds). We also show that the Gilbert damping and inertial damping are related to one another through the imaginary and real parts of the magnetic susceptibility tensor respectively.

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“…The last term in the Hamiltonian H ext soc describes the interaction of the photon spin angular momentum density, j s = ǫ 0 (E × A) [41], with the electron spins [40,42]. A related interaction energy due to a coupling of the angular momentum density of the electromagnetic field with the magnetic moment was proposed recently on phenomenological grounds [43].…”

Section: Spin Equation Of Motionmentioning

confidence: 99%

Relativistic theory of spin relaxation mechanisms in the Landau-Lifshitz-Gilbert equation of spin dynamics

2016

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Starting from the Dirac-Kohn-Sham equation we derive the relativistic equation of motion of spin angular momentum in a magnetic solid under an external electromagnetic field. This equation of motion can be rewritten in the form of the well-known Landau-Lifshitz-Gilbert equation for a harmonic external magnetic field, and leads to a more general magnetization dynamics equation for a general time-dependent magnetic field. In both cases with an electronic spin-relaxation term which stems from the spin-orbit interaction. We thus rigorously derive, from fundamental principles, a general expression for the anisotropic damping tensor which is shown to contain an isotropic Gilbert contribution as well as an anisotropic Ising-like and a chiral, Dzyaloshinskii-Moriya-like contribution. The expression for the spin relaxation tensor comprises furthermore both electronic interband and intraband transitions. We also show that when the externally applied electromagnetic field possesses spin angular momentum, this will lead to an optical spin torque exerted on the spin moment.

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Electron-spin dynamics induced by photon spins

Cited by 27 publications

References 41 publications

Theory of radiative electron polarization in strong laser fields

Theory of radiative electron polarization in strong laser fields

Relativistic theory of magnetic inertia in ultrafast spin dynamics

Relativistic theory of spin relaxation mechanisms in the Landau-Lifshitz-Gilbert equation of spin dynamics

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