Analytical treatment of ultrafast laser-induced spin-flippingΛprocesses on magnetic nanostructures

Abstract

In this paper, we analytically treat ultrafast, laser-induced, spin-flipping processes based on model systems with triplet ground state. After obtaining the wave functions, we give analytical solutions for the induced material polarization in the time domain. Compact summation formulas for the time-dependent (windowed) induced polarization of the material in the frequency domain, as well as its helicity (fourth Stokes parameter), are given. These solutions compare excellently with numerical results obtained for realistic systems (i.e., systems that can or have been synthesized and were treated with high-level quantum chemical methods including electron correlations and relativistic effects). We thus analytically show that laser-induced spin flip is possible and can be detected from the helicity of the emitted light during the process. Additionally, we analyze the effects of a finite temperature and the time window of a measuring apparatus on the signal detected. These are very crucial steps not only for verifying the validity of previous numerical results, but also for the deeper understanding of the physical mechanisms involved.

Infrared and electronic absorption spectra as well as ultrafast spin dynamics in isolatedCo3+(EtOH)andCo3+(EtOH,Jin1, Becherer2, Bellaire3 et al. 2014Phys. Rev. BSelf Cite240200View full textAdd to dashboardCite

“…The observed trend agrees with the analytical result on a three-level model system in Ref. [37], and most importantly, exhibits richer features due to the quantum interference.…”

“…As expected, despite their distinct dynamical features, the three spin-flip scenarios always take place on the ligand-free Co atom, which always exhibits the highest degree of spin localization. The parameters of the optimized laser pulses of these three scenarios are listed in Table I state [37], the fact that the optimized laser energy of each scenario is almost resonant with the energy difference between the initial (final) and the intermediate state can be easily understood.…”

Relation between magnetization and Faraday angles produced by ultrafast spin-flip processes within the three-level Λ-type system

“…In order to calculate the polarization and the magnetization, we need to model the excited material. Following Lefkidis and H€ ubner, 18 the active medium is described by a three-level system, as shown schematically in Fig. 2 j3i, and the states j2i and j3i.…”

“…In recent years, various spin-flip processes have been suggested, highlighting the role played by phonons, 4 magnons, 5 the spin-orbit coupling (SOC), [6][7][8] or the helicity transfer of the incident light. 9 Alternative studies propose the relativistic coupling between spins and photons, as a coherent process occurring during the propagation of the laser pulse. 10,11 Besides the previous fundamental aspects, another problematic issue has recently appeared, concerning the question of whether or not the experimental time-resolved magnetooptical (MO) signal really reflects the magnetization dynamics on the subpicosecond time-scale.…”

“…V C 2015 AIP Publishing LLC 118, 053908-1 JOURNAL OF APPLIED PHYSICS 118, 053908 (2015) magneto-optical effects induced by ultrafast laser pulses. Recently, Lefkidis and H€ ubner 18 have theoretically analyzed laser-induced spin-flip processes based on K-type systems. They have shown that their analytical results were consistent with those already obtained using numerical approaches on more realistic systems.…”