Interface reflectivity of a superdiffusive spin current in ultrafast demagnetization and terahertz emission

Lu, W.-T.; Zhao, Yawen; Battiato, Marco; Wu, Yongkang; Yuan, Zhe

doi:10.1103/physrevb.101.014435

Cited by 33 publications

(38 citation statements)

References 57 publications

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“…This breakthrough highlighted that interfaces leading to large spin transfer torque are also excellent emitters of electromagnetic waves [8][9][10][11][12] . Theoretical simulations based on superdiffusive transport equations have successfully reproduced the observed emission 13,14 . However, these frameworks do not cover the impact of the electronic transmission at interfaces, neither the discussion of the particular role of the interfacial spin-orbit fields originating from charge transfer and symmetry breaking 15 .…”

Section: Introductionmentioning

confidence: 79%

Spin injection efficiency at metallic interfaces probed by THz emission spectroscopy

Hawecker¹,

Dang²,

Rongione³

et al. 2021

Preprint

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Terahertz (THz) spin-to-charge conversion has become an increasingly important process for THz pulse generation and as a tool to probe ultrafast spin interactions at magnetic interfaces. However, its relation to traditional, steady state, ferromagnetic resonance techniques is poorly understood.Here we investigate nanometric trilayers of Co/X/Pt (X=Ti, Au or Au0:85W0:15) as a function of the 'X' layer thickness, where THz emission generated by the inverse spin Hall effect is compared to the Gilbert damping of the ferromagnetic resonance. Through the insertion of the 'X' layer we show that the ultrafast spin current injected in the non-magnetic layer defines a direct spin conductance, whereas the Gilbert damping leads to an effective spin mixing-conductance of the trilayer. Importantly, we show that these two parameters are connected to each other and that spinmemory losses can be modeled via an effective Hamiltonian with Rashba fields. This work highlights that magneto-circuits concepts can be successfully extended to ultrafast spintronic devices, as well as enhancing the understanding of spin-to-charge conversion processes through the complementarity between ultrafast THz spectroscopy and steady state techniques.

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Section: Introductionmentioning

confidence: 79%

Spin injection efficiency at metallic interfaces probed by THz emission spectroscopy

Hawecker¹,

Dang²,

Rongione³

et al. 2021

Preprint

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“…The excitation of a magnetic sample by an ultrafast optical pulse, as described above, leads to an increase in the average electron (spin) velocity. There are many different methods for calculating or simulating the resulting electronic and spin transport, but most analyses start from Boltzmann transport [82][83][84][85] . The key conceptual idea of Boltzmann transport relevant to spintronic THz emission is that the high density of excited (high momentum) electrons resulting from the optical excitation will result in a flow of electrons (spins) into unexcited regions (e.g.…”

Section: Ultrafast Spin Transportmentioning

confidence: 99%

“…Right after the laser excitation, electron transport can be described in the ballistic limit. The transport characteristics then gradually change and approach the diffusive regime 85 with a timeconstant determined by the scattering rate. Superdiffusive spin transport 82,83,85 is observed in the transition between the ballistic and diffusive transport regimes: most electrons scatter and create secondary electrons, while some electrons propagate ballistically 5 .…”

Section: Ultrafast Spin Transportmentioning

confidence: 99%

“…The transport characteristics then gradually change and approach the diffusive regime 85 with a timeconstant determined by the scattering rate. Superdiffusive spin transport 82,83,85 is observed in the transition between the ballistic and diffusive transport regimes: most electrons scatter and create secondary electrons, while some electrons propagate ballistically 5 . The recent work of Nenno and coauthors provides a nice example of how simulations of the hot-carrier dynamics following laser excitation of bilayers containing a ferromagnetic metal (FM) and a normal metal (NM) can be used to predict and understand the resulting THz emission 84 .…”

Section: Ultrafast Spin Transportmentioning

confidence: 99%

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Principles of spintronic THz emitters

Wu,

Ameyaw,

Doty

et al. 2021

Preprint

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Significant progress has been made in answering fundamental questions about how and, more importantly, on what time scales interactions between electrons, spins, and phonons occur in solid state materials. These complex interactions are leading to the first real applications of terahertz (THz) spintronics: THz emitters that can compete with traditional THz sources and provide additional functionalities enabled by the spin degree of freedom. This tutorial article is intended to provide the background necessary to understand, use, and improve THz spintronic emitters. A particular focus is the introduction of the physical effects that underlie the operation of spintronic THz emitters. These effects were, for the most part, first discovered through traditional spin-transport and spintronic studies. We therefore begin with a review of the historical background and current theoretical understanding of ultrafast spin physics that has been developed over the past twenty-five years. We then discuss standard experimental techniques for the characterization of spintronic THz emitters and -more broadly -ultrafast magnetic phenomena. We next present the principles and methods of the synthesis and fabrication of various types of spintronic THz emitters. Finally, we review recent developments in this exciting field including the integration of novel material platforms such as topological insulators as well as antiferromagnets and materials with unconventional spin textures.

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“…(2) applying spin-and material-dependent interface reflectivities R σ M based on first-principles to account for the partial reflection of the currents at the interface [22]. To conserve charge neutrality, a current of the same amount has to flow back into the magnetic layer.…”

mentioning

confidence: 99%

Control of transport phenomena in magnetic heterostructures by wavelength modulation

Seibel¹,

Marius²,

Stiehl³

et al. 2021

Preprint

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We demonstrate the tuneablity of the ultrafast energy flow in magnetic/non-magnetic bilayer structures by changing the wavelength of the optical excitation. This is achieved by an advanced description of the temperature based µT-model that explicitly considers the wavelength-and layerdependent absorption profile within multilayer structures. For the exemplary case of a Ni/Au bilayer, our simulations predict that the energy flow from Ni to Au is reversed when changing the wavelength of the excitation from the infrared to the ultraviolet spectral range. These predictions are fully supported by characteristic signatures in the magneto-optical Kerr traces of the Ni/Au model system. Our results will open up new avenues to steer and control the energy transport in designed magnetic multilayer for ultrafast spintronic applications.

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Interface reflectivity of a superdiffusive spin current in ultrafast demagnetization and terahertz emission

Cited by 33 publications

References 57 publications

Spin injection efficiency at metallic interfaces probed by THz emission spectroscopy

Spin injection efficiency at metallic interfaces probed by THz emission spectroscopy

Principles of spintronic THz emitters

Control of transport phenomena in magnetic heterostructures by wavelength modulation

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