Laser-Induced Intersite Spin Transfer

Dewhurst, J. K.; Elliott, Peter; Shallcross, S.; Gross, E. K. U.; Sharma, S.

doi:10.1021/acs.nanolett.7b05118

Cited by 175 publications

(180 citation statements)

References 54 publications

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“…semiconductor magnetism | ultrafast | quantum simulation | angular momentum U ltrafast manipulation of magnetic order is important for high-speed information storage devices (1). Over the past 2 decades, there have been considerable interests in exploring and understanding the control of spin dynamics by femtosecond laser (2)(3)(4)(5)(6)(7)(8)(9)(10). Light-induced ultrafast demagnetization has been found in a broad class of materials from ferromagnetic metals, semiconductors, and clusters to antiferromagnetic dielectrics (1,(11)(12)(13)(14)(15)(16).…”

Section: Ultrafast Control Of Magnetic Order By Light Provides a Prommentioning

confidence: 99%

Revealing angular momentum transfer channels and timescales in the ultrafast demagnetization process of ferromagnetic semiconductors

Chen

Luo

Wang

2019

Proc. Natl. Acad. Sci. U.S.A.

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Ultrafast control of magnetic order by light provides a promising realization for spintronic devices beyond Moore’s Law and has stimulated intense research interest in recent years. Yet, despite 2 decades of debates, the key question of how the spin angular momentum flows on the femtosecond timescale remains open. The lack of direct first-principle methods and pictures for such process exacerbates the issue. Here, we unravel the laser-induced demagnetization mechanism of ferromagnetic semiconductor GaMnAs, using an efficient time-dependent density functional theory approach that enables the direct real-time snapshot of the demagnetization process. Our results show a clear spin-transfer trajectory from the localized Mn-d electrons to itinerant carriers within 20 fs, illustrating the dominant role of sp−d interaction. We find that the total spin of localized electrons and itinerant carriers is not conserved in the presence of spin-orbit coupling (SOC). Immediately after laser excitation, a growing percentage of spin-angular momentum is quickly transferred to the electron orbital via SOC in about 1 ps, then slowly to the lattice via electron–phonon coupling in a few picoseconds, responsible for the 2-stage process observed experimentally. The spin-relaxation time via SOC is about 300 fs for itinerant carriers and about 700 fs for Mn-d electrons. These results provide a quantum-mechanical microscopic picture for the long-standing questions regarding the channels and timescales of spin transfer, as well as the roles of different interactions underlying the GaMnAs demagnetization process.

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Section: Ultrafast Control Of Magnetic Order By Light Provides a Prommentioning

confidence: 99%

Revealing angular momentum transfer channels and timescales in the ultrafast demagnetization process of ferromagnetic semiconductors

Chen

Luo

Wang

2019

Proc. Natl. Acad. Sci. U.S.A.

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“…However, visible lasers probe the net magnetization averaged over all elements in the material. Very recent theoretical papers exploring laser-excited Heusler compounds have suggested the possibility of light-induced spin transfer from one element to another on extremely fast (<10 fs) time scales (13,14). This could, in theory, enable the ultimate goal of ultrafast direct optical manipulation of the magnetic state of a material, provided these dynamics can be observed.…”

Section: Introductionmentioning

confidence: 99%

Direct light–induced spin transfer between different elements in a spintronic Heusler material via femtosecond laser excitation

et al. 2020

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Heusler compounds are exciting materials for future spintronics applications because they display a wide range of tunable electronic and magnetic interactions. Here, we use a femtosecond laser to directly transfer spin polarization from one element to another in a half-metallic Heusler material, Co2MnGe. This spin transfer initiates as soon as light is incident on the material, demonstrating spatial transfer of angular momentum between neighboring atomic sites on time scales < 10 fs. Using ultrafast high harmonic pulses to simultaneously and independently probe the magnetic state of two elements during laser excitation, we find that the magnetization of Co is enhanced, while that of Mn rapidly quenches. Density functional theory calculations show that the optical excitation directly transfers spin from one magnetic sublattice to another through preferred spin-polarized excitation pathways. This direct manipulation of spins via light provides a path toward spintronic devices that can operate on few-femtosecond or faster time scales.

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“…Prominent examples include all-optical magnetization switching mediated by a transient ferromagnetic state 1,2 , control of antiferromagnetic order [3][4][5][6][7] and transfer of angular momentum via terahertz spin currents [8][9][10][11][12][13] . Very recently it was shown theoretically, that in multi-component magnetic systems laser-driven optical transitions can induce a spin-selective charge flow between sub-lattices causing significant magnetization changes, including switching from antiferromagnetic to ferromagnetic order [14][15][16][17][18] . Indeed, a first experiment employing attosecond spectroscopy in the extreme ultraviolet spectral range (XUV) was able to demonstrate how a light-field driven coherent charge relocation leads to an ultrafast loss of magnetization 19 .…”

mentioning

confidence: 99%

Optical inter-site spin transfer probed by energy and spin-resolved transient absorption spectroscopy

et al. 2020

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Optically driven spin transport is the fastest and most efficient process to manipulate macroscopic magnetization as it does not rely on secondary mechanisms to dissipate angular momentum. In the present work, we show that such an optical inter-site spin transfer (OISTR) from Pt to Co emerges as a dominant mechanism governing the ultrafast magnetization dynamics of a CoPt alloy. To demonstrate this, we perform a joint theoretical and experimental investigation to determine the transient changes of the helicity dependent absorption in the extreme ultraviolet spectral range. We show that the helicity dependent absorption is directly related to changes of the transient spin-split density of states, allowing us to link the origin of OISTR to the available minority states above the Fermi level. This makes OISTR a general phenomenon in optical manipulation of multi-component magnetic systems.

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Laser-Induced Intersite Spin Transfer

Cited by 175 publications

References 54 publications

Revealing angular momentum transfer channels and timescales in the ultrafast demagnetization process of ferromagnetic semiconductors

Revealing angular momentum transfer channels and timescales in the ultrafast demagnetization process of ferromagnetic semiconductors

Direct light–induced spin transfer between different elements in a spintronic Heusler material via femtosecond laser excitation

Optical inter-site spin transfer probed by energy and spin-resolved transient absorption spectroscopy

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