Regensburg 2022 – scientific programme

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MA: Fachverband Magnetismus

MA 8: Ultrafast Magnetization Effects 1

MA 8.11: Talk

Monday, September 5, 2022, 17:30–17:45, H37

Ultrafast spin dynamics: complementing theoretical analyses by quantum state measures — Franziska Ziolkowski, •Oliver Busch, Jürgen Henk, and Ingrid Mertig — Institut für Physik, Martin-Luther-Universität, D-06099 Halle

In theoretical studies of ultrafast spin dynamics, one usually analyses and discusses observables — such as magnetization. On top of this, quantum state (QS) measures defined for density matrices may provide additional valuable insights into the dynamics [1].

We report on a study on QS measures that complement simulations of ultrafast spin dynamics [2]. For a Co/Cu heterostructure which is excited by a femtosecond laser pulse and coupled to a bosonic heat bath, we discuss the time dependence of QS measures, in particular distances in Hilbert space and degree of purity in the density matrix [3].

We identify observables and modifications of the investigated system to which both the distance and the purity measures are in particular sensitive: the polarization of the laser pulse and the composition of the sample. In contrast, temperature and photon energy affect the QS measures mildly. Our study shows that QS measures are complementary and beneficial quantities for spin dynamics simulations.

[1] S. Barnett, Quantum Information (Oxford University Press, Oxford, 2009)

[2] F. Töpler et al.; New Journal of Physics 23, 033042 (2021)

[3] R. Jozsa, Fidelity for Mixed Quantum States, Journal of Modern Optics 41, 2315 (1994)