Controlling electron spin dynamics in bichromatic Kapitza-Dirac scattering by the laser field polarization

Dellweg, Matthias M.; Müller, Carsten

doi:10.1103/physreva.95.042124

Cited by 24 publications

(23 citation statements)

References 44 publications

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“…(A6) which is fitting to the time in Eq. (49). This demonstrates that the considerations in appendix A are suitable for relating the quantum dynamics of different time-dependent field amplitudes to each other.…”

Section: E Distinct Spin Separationmentioning

confidence: 67%

“…Note that at the final stage of our research spindependent diffraction has been discussed in the context of a three-photon interaction in the Kapitza-Dirac effect [48,49]. The former setup [48] makes use of an interferometric setup with linear polarized laser beams, which combines three-photon and two-photon Kapitza-Dirac scattering, while the latter setup [49] solely considers three-photon scattering in laser fields with a general polarization description. The effective three-photon interaction is realized by employing a bi-chromatic standing light wave as external field.…”

Section: Introductionmentioning

confidence: 99%

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Electron-spin filter and polarizer in a standing light wave

Ahrens

2017

Phys. Rev. A

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We demonstrate the theoretical feasibility of spin-dependent diffraction and spin-polarization of an electron in two counter-propagating, circularly polarized laser beams. The spin-dynamics appears in a two-photon process of the Kapitza-Dirac effect in the Bragg regime. We show the spin-dependence of the diffraction process by comparison of the time-evolution of a spin-up and spin-down electron in a relativistic quantum simulation. We further discuss the spin properties of the scattering by studying an analytically approximated solution of the time-evolution matrix. A classification scheme in terms of unitary or non-unitary propagation matrices is used for establishing a generalized and spin-independent description of the spin properties in the diffraction process.

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Section: E Distinct Spin Separationmentioning

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Electron-spin filter and polarizer in a standing light wave

Ahrens

2017

Phys. Rev. A

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“…For instance, we approximate the moving averages in the pre-exponential in Eqs. (40) and (39) to lowest order as ḣ ḣ (τ ), because for very short averaging intervals the moving average approaches the value at the midpoint. In addition, in the off-diagonal terms we may use δh 0 for locally constant fields, see Appendix B.…”

Section: A Local Constant Field Approximationmentioning

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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“…in which / A is denoted by Feynman slash / A = γ.A and γ stands for Dirac matrices. An analytical treatment for multiphoton stimulated Compton scattering such as bichromatic Kapitza-Dirac scattering has been accomplished through S matrix approach with suitable approximations [22]. The Dirac equation has a well known solution; Volkov state for an electron in the case of the external potential being a plane wave.…”

Section: B S Matrix Approachmentioning

confidence: 99%

Four-photon Kapitza-Dirac effect as an electron spin filter

2018

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We theoretically demonstrate the feasibility of producing electron beam splitter using Kapitza-Dirac diffraction on bichromatic standing waves which are created by the fundamental frequency and the third harmonic. The relativistic electron in Bragg regime absorbs three photons with frequency of ω and emits a photon with frequency of 3ω, four-photon Kapitza-Dirac effect. In this four-photon Kapitza-Dirac effect distinct spin effects arise in different polarizations of the third harmonic laser beam. It is shown that the shape of Rabi oscillation between initial and scattered states is changed and finds two unequal peaks. In circular polarization for fundamental and third harmonic, despite Rabi oscillation, the spin down electron in 0.56 fs intervals maintains its momentum and spin. Also we present an electron spin filter with combination of a linearly polarized fundamental laser beam and a third harmonic with circular polarization that scatters the electron beam according to its spin state.

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Controlling electron spin dynamics in bichromatic Kapitza-Dirac scattering by the laser field polarization

Cited by 24 publications

References 44 publications

Electron-spin filter and polarizer in a standing light wave

Electron-spin filter and polarizer in a standing light wave

Theory of radiative electron polarization in strong laser fields

Four-photon Kapitza-Dirac effect as an electron spin filter

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