Review of Ultrafast Demagnetization After Femtosecond Laser Pulses: A Complex Interaction of Light with Quantum Matter
American Journal of Modern Physics
Volume 7, Issue 2, March 2018, Pages: 68-74
Received: Dec. 27, 2017;
Accepted: Jan. 9, 2018;
Published: Jan. 18, 2018
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Manfred Fähnle, Max Plank Institute for Intelligent Systems, Stuttgart, Germany
Michael Haag, Max Plank Institute for Intelligent Systems, Stuttgart, Germany
Christian Illg, Max Plank Institute for Intelligent Systems, Stuttgart, Germany
Benedikt Mueller, Max Plank Institute for Intelligent Systems, Stuttgart, Germany
Weikai Weng, Max Plank Institute for Intelligent Systems, Stuttgart, Germany
Theodoros Tsatsoulis, Max Plank Institute for Intelligent Systems, Stuttgart, Germany
Haonan Huang, Max Plank Institute for Intelligent Systems, Stuttgart, Germany
Johan Briones, Max Plank Institute for Intelligent Systems, Stuttgart, Germany
Nicolas Teeny, Max Plank Institute for Intelligent Systems, Stuttgart, Germany
Lifa Zhang, Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing, China
Tilmann Kuhn, Institute of Solid State Theory, University of Münster, Münster, Germany
When a magnetic film is excited by a femtosecond laser pulse, either with THz or with optical frequencies, then there is at least a partial demagnetization within a few hundred femtoseconds, followed by a remagnetization to the original state on a bit longer time scale. This phenomenon is caused by a complex interaction of light with quantum matter. This paper gives a review of the present knowledge of the underlying physics. It discusses first the situation of a direct change of the magnetization by its interaction with the electromagnetic wave of the laser pulse, which appears during THz laser pulses with small field amplitudes. Then it considers the situation of an indirect change which appears after THz laser pulses with large field amplitudes and after optical laser pulses. In these cases the laser photons primarily excite electrons, with subsequent modifications of their spin-angular momenta by spin-flip scatterings of these electrons at quasiparticles, either at other electrons or at phonons or at magnons. The contributions of these various spin-flip scatterings to demagnetization are investigated. Then the transfer of angular momentum from the electronic spin system to the lattice during ultrafast demagnetization is discussed by describing the lattice vibrations in terms of magnetoelastic spin-phonon modes. Finally, the effect of electronic correlations in the sense of the density-matrix theory is investigated.
Review of Ultrafast Demagnetization After Femtosecond Laser Pulses: A Complex Interaction of Light with Quantum Matter, American Journal of Modern Physics.
Vol. 7, No. 2,
2018, pp. 68-74.
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