Ultrafast strain engineering and coherent structural dynamics from resonantly driven optical phonons in LaAlO3

Hortensius, J. R.; Afanasiev, D.; Sasani, Alireza; Bousquet, Éric; Caviglia, Andrea D.

doi:10.1038/s41535-020-00297-z

Cited by 16 publications

(9 citation statements)

References 51 publications

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“…In both geometries, the pump-induced rotation of the probe polarization plane, originating from the Faraday effect (θF) or the MOKE (θK), is tracked as a function of the pump-probe time delay. Note that while the Faraday transmission geometry is routinely used in pump-probe experiments for detecting uniform (k = 0) spin precession in antiferromagnets 19 , the reflection geometry has been shown to enable detection of finite-k coherent excitations such as propagating acoustic wavefronts 26,27 . As shown below we demonstrate that the reflection geometry can be also used to probe the dynamics of short-wavelength propagating coherent spin waves.…”

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confidence: 99%

Coherent spin-wave transport in an antiferromagnet

et al. 2021

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Magnonics is a research field complementary to spintronics, in which the quanta of spin waves (magnons) replace electrons as information carriers, promising less energy dissipation 1-3 . The development of ultrafast nanoscale magnonic logic circuits calls for new tools and materials to generate coherent spin waves with frequencies as high, and wavelengths as short, as possible 4,5 . Antiferromagnets can host spin waves at THz frequencies and are therefore seen as a future platform for the fastest and the least dissipative transfer of information 6-11 . However, the generation of short-wavelength coherent propagating magnons in antiferromagnets has so far remained elusive. Here we report the efficient emission and detection of a nanometer-scale wavepacket of coherent propagating magnons in antiferromagnetic DyFeO3 using ultrashort pulses of light. The subwavelength confinement of the laser field due to large absorption creates a strongly nonuniform spin excitation profile, enabling the propagation of a broadband continuum of coherent THz spin waves. The wavepacket features magnons with detected wavelengths down to 125 nm that propagate with supersonic velocities of more than 13 km/s into the material. The long-sought source of coherent shortwavelength spin carriers demonstrated here opens up new prospects for THz antiferromagnetic magnonics and coherence-mediated logic devices at THz frequencies.Antiferromagnetic insulators (AFMs) are prime candidates to replace ferromagnets (FMs) as active media in the quest towards high-speed spin transport and large spectral bandwidth operation [6][7][8] . Integration of AFMs in future wave-based technologies 3 crucially requires the realization of coherent (ballistic) transport of antiferromagnetic spin waves over large distances 5 . In this regard, non-uniform spin-wave modes with short wavelengths (λ ≲ 100 nm) are of particular importance: they can operate at THz clock rates, exhibit high propagation velocities and enable the miniaturization of devices down to the nanoscale. Phase-coherent ballistic spin transport in AFMs

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confidence: 99%

Coherent spin-wave transport in an antiferromagnet

et al. 2021

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“…In that study, oscillations of the pumped mode were not measured via time-resolved spectroscopy experiments to show that IR-active phonon excitations, and not electronic excitations, are responsible for the coherent oscillations of the Raman-active phonons. However, coherent oscillations at Raman-active phonon frequencies have been observed in insulating ErFeO 3 [14] and LaAlO 3 [15] in timeresolved spectroscopy experiments after a mid-IR pump, and these experiments do show that the amplitude of the oscillations are largest when the pump frequency is tuned to the frequency of the IR-active phonon mode. Moreover, oscillations of the pumped mode as well as the nonlinearly coupled low-frequency mode have been simultaneously observed after a mid-IR pump in time-resolved second harmonic generation (SHG) experiment on LiNbO 3 [16], which conclusively demonstrates the phenonmenon of stimulated ionic Raman scattering.…”

Section: Introductionmentioning

confidence: 98%

Light-control of materials via nonlinear phononics

Subedi¹

2021

Comptes Rendus. Physique

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Nonlinear phononics is the phenomenon in which a coherent dynamics in a material along a set of phonons is launched after its infrared-active phonons are selectively excited using external light pulses. The microscopic mechanism underlying this phenomenon is the nonlinear coupling of the pumped infraredactive mode to other phonon modes present in a material. Nonlinear phonon couplings can cause finite time-averaged atomic displacements with or without broken crystal symmetries depending on the order, magnitude and sign of the nonlinearities. Such coherent lattice displacements along phonon coordinates can be used to control the physical properties of materials and even induce transient phases with lower symmetries. Light-control of materials via nonlinear phononics has become a practical reality due to the availability of intense mid-infrared lasers that can drive large-amplitude oscillations of the infrared-active phonons of materials. Mid-infrared pump induced insulator-metal transitions and spin and orbital order melting have been observed in pump-probe experiments. First principles based microscopic theory of nonlinear phononics has been developed, and it has been used to better understand how the lattice evolves after a mid-infrared pump excitation of infrared-active phonons. This theory has been used to predict lightinduced switching of ferroelectric polarization as well as ferroelectricity in paraelectrics and ferromagnetism in antiferromagnets, which have been partially confirmed in recent experiments. This review summarizes the experimental and theoretical developments within this emerging field.

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“…However, the sub-picosecond time resolution is only possible with mega-science facilities such as synchrotron radiation sources or free-electron lasers 15 . The development of optical methods (such as Raman scattering 16 , 17 or phonon spectroscopy 7 , 18 , 19 for registering structural changes in matter is an essential direction in developing express methods of structural diagnosis with high spatial and temporal resolution. This method can be used and spread more widely, making the developed approach highly relevant to condensed matter physics 11 , 20 .…”

Section: Introductionmentioning

confidence: 99%

Dynamics of ultrafast phase transitions in MgF2 triggered by laser-induced THz coherent phonons

Mareev

Potemkin

2022

Sci Rep

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The advent of free-electron lasers opens new routes for experimental high-pressure physics, which allows studying dynamics of condensed matter with femtosecond resolution. A rapid compression, that can be caused by laser-induced shock impact, leads to the cascade of high-pressure phase transitions. Despite many decades of study, a complete understanding of the lattice response to such a compression remains elusive. Moreover, in the dynamical case (in contrast to quasi-static loading) the thresholds of phase transitions can change significantly. Using the third harmonic pump–probe technique combined with molecular dynamics to simulate the terahertz (THz) spectrum, we revealed the dynamics of ultrafast laser-induced phase transitions in MgF2 in all-optical experiment. Tight focusing of femtosecond laser pulse into the transparent medium leads to the generation of sub-TPa shock waves and THz coherent phonons. The laser-induced shock wave propagation drastically displaces atoms in the lattice, which leads to phase transitions. We registered a cascade of ultrafast laser-induced phase transitions (P42/mnm ⇒ Pa-3 ⇒ Pnam) in magnesium fluoride as a change in the spectrum of coherent phonons. The phase transition has the characteristic time of 5–10 ps, and the lifetime of each phase is on the order of 40–60 ps. In addition, phonon density of states, simulated by molecular dynamics, together with third-harmonic time-resolved spectra prove that laser-excited phonons in a bulk of dielectrics are generated by displacive excitation (DECP) mechanism in plasma mediated conditions.

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Ultrafast strain engineering and coherent structural dynamics from resonantly driven optical phonons in LaAlO3

Cited by 16 publications

References 51 publications

Coherent spin-wave transport in an antiferromagnet

Coherent spin-wave transport in an antiferromagnet

Light-control of materials via nonlinear phononics

Dynamics of ultrafast phase transitions in MgF2 triggered by laser-induced THz coherent phonons

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