期刊
PHYSICAL REVIEW B
卷 100, 期 2, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.100.024428
关键词
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资金
- Japanese Society for Promotion of Science (JSPS) [P16326]
- Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)
- Stichting voor Fundamenteel Onderzoek der Materie (FOM)
- ERC [339813]
- LASERLAB-EUROPE [284464, 654148]
- Russian Science Foundation [16-12-10456]
- European Research Council (ERC) [338957]
- Humboldt Foundation
- EU ERC [268066]
- Transregional Collaborative Research Center [(SFB/TRR) 173]
- European Union [696656]
- Shell-NWO/FOM-initiative Computational sciences for energy research of Shell
- Chemical Sciences, Earth and Life Sciences, Physical Sciences, FOM
- Chemical Sciences, Earth and Life Sciences, Physical Sciences, STW
- Russian Science Foundation [19-12-13020] Funding Source: Russian Science Foundation
- European Research Council (ERC) [268066, 339813] Funding Source: European Research Council (ERC)
The impulsive generation of two-magnon modes in antiferromagnets by femtosecond optical pulses, so-called femto-nanomagnons, leads to coherent longitudinal oscillations of the antiferromagnetic order parameter that cannot be described by a thermodynamic Landau-Lifshitz approach. We argue that this dynamics is triggered as a result of a laser-induced modification of the exchange interaction. In order to describe the oscillations, we have formulated a quantum mechanical description in terms of magnon pair operators and coherent states. Such an approach allowed us to derive an effective macroscopic equation of motion for the temporal evolution of the antiferromagnetic order parameter. An implication of the latter is that the photoinduced spin dynamics represents a macroscopic entanglement of pairs of magnons with femtosecond period and nanometer wavelength. By performing magneto-optical pump-probe experiments with 10 femtosecond resolution in the cubic KNiF3 and the uniaxial K2NiF4 collinear Heisenberg antiferromagnets, we observed coherent oscillations at the frequency of 22 and 16 THz, respectively. The detected frequencies as a function of the temperature fit the two-magnon excitation up to the Neel point. The experimental signals are described as dynamics of magnetic linear dichroism due to longitudinal oscillations of the antiferromagnetic vector.
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