Polarized phonons carry the missing angular momentum in femtosecond demagnetization

Abstract

Magnetic phenomena are ubiquitous in our surroundings and indispensable for modern science and technology, but it is notoriously difficult to change the magnetic order of a material in a rapid way. However, if a thin nickel film is subjected to ultrashort laser pulses, it can lose its magnetic order almost completely within merely femtosecond times. This phenomenon, in the meantime also observed in many other materials, has connected magnetism with femtosecond optics in an efficient, ultrafast and complex way, offering opportunities for rapid information processing or ultrafast spintronics at frequencies approaching those of light. Consequently, the physics of ultrafast demagnetization is central to modern material research, but a crucial question has remained elusive: If a material loses its magnetization within only femtoseconds, where is the missing angular momentum in such short time? Here we use ultrafast electron diffraction to reveal in nickel an almost instantaneous, long-lasting, non-equilibrium population of anisotropic high-frequency phonons that appear as quickly as the magnetic order is lost. The anisotropy plane is perpendicular to the direction of the initial magnetization and the atomic oscillation amplitude is 2 pm. We explain these observations by means of circularly polarized phonons that quickly absorb the missing angular momentum of the spin system before the slower onset of a macroscopic sample rotation. The time that is needed for demagnetization is related to the time it takes to accelerate the atoms. These results provide an atomistic picture of ultrafast demagnetization under adherence to all conservation laws but also demonstrate the general importance of polarized phonons for non-equilibrium dynamics and provide innovative ways for controlling materials on atomic dimensions.

References in corpus (2)

• Super-Diffusive Spin-Transport as a Mechanism of Ultrafast Demagnetization
• Local magnetic moments in iron and nickel at ambient and Earth's core conditions

Cited by in corpus (78)

• Chiral phonons probed by X rays
• Terahertz electric-field driven dynamical multiferroicity in SrTiO${}_3$
• Large effective magnetic fields from chiral phonons in rare-earth halides
• Phononic Switching of Magnetization by the Ultrafast Barnett Effect
• Chirality selective magnon-phonon hybridization and magnon-induced chiral phonons in a layered zigzag antiferromagnet
• Attosecond magnetization dynamics in non-magnetic materials driven by intense femtosecond lasers
• Electron magnetic moment of transient chiral phonons in KTaO${}_3$
• Light-induced hexatic state in a layered quantum material
• Inertial effects in ultrafast spin dynamics
• Magnetic order induced chiral phonons in a ferromagnetic Weyl semimetal
• Orbital Pumping Incorporating Both Orbital Angular Momentum and Position
• Observation of Phonon Angular Momentum
• Angular momentum transfer via relativistic spin-lattice coupling from first principles
• Ultrafast demagnetization in ferromagnetic materials: Origins and progress
• Spin current driven by ultrafast magnetization of FeRh
• The interplay of local electron correlations and ultrafast spin dynamics in fcc Ni
• Ultrafast element- and depth-resolved magnetization dynamics probed by transverse magneto-optical Kerr effect spectroscopy in the soft x-ray range
• Phonon-induced geometric chirality
• Phonon Inverse Faraday effect from electron-phonon coupling
• Weyl Phonons: The connection of topology and chirality
• Ab initio investigation of laser-induced ultrafast demagnetization of L1${}_0$ FePt: Intensity dependence and importance of electron coherence
• Strain-induced activation of chiral-phonon emission in monolayer WS${}_2$
• Ultrafast Demagnetization through Femtosecond Generation of Non-thermal Magnons
• Electric field-induced nonreciprocal spin current due to chiral phonons in chiral-structure superconductors
• Magnetic nutation: transient separation of magnetization from its angular momentum
• Ultrafast magnetization reversal in ferromagnetic spin-valves: an s-d model perspective
• Relativistic ultrafast electron diffraction at high repetition rates
• Charge and spin current pumping by ultrafast demagnetization dynamics
• Electron-phonon mediated spin-flip as driving mechanism for ultrafast magnetization dynamics in 3$d$ ferromagnets
• Rotationally invariant formulation of spin-lattice coupling in multi-scale modeling
• Magnetic switching of phonon angular momentum in a ferrimagnetic insulator
• Abnormal Phonon Angular Momentum due to Off-diagonal Elements in Density Matrix induced by Temperature Gradient
• Quantum-classical approach to spin and charge pumping and the ensuing radiation in THz spintronics: Example of ultrafast-light-driven Weyl antiferromagnet Mn${}_3$Sn
• Ultrafast Spin Dynamics and Photoinduced Insulator-to-Metal Transition in $\alpha$-$RuC{l}_3$
• Theory of spin magnetization driven by chiral phonons
• Unconventional magnetism mediated by spin-phonon-photon coupling
• Emergent Phenomena with Broken Parity-Time Symmetry: Odd-order vs. Even-order Effects
• Chiral phonons in polar LiNbO3
• Time-domain study of coupled collective excitations in quantum materials
• Momentum, spin, and orbital angular momentum of electromagnetic, acoustic, and water waves
• Calculating spin-lattice interactions in ferro- and antiferromagnets: the role of symmetry, dimension and frustration
• Spin Resonance Spectroscopy with an Electron Microscope
• Generation of Phonons with Angular Momentum During Ultrafast Demagnetization
• Terahertz Control of Linear and Nonlinear Magno-Phononics
• Enhanced Magnetization by Defect-Assisted Exciton Recombination in Atomically Thin CrCl${}_3$
• Electrically Controllable Chiral Phonons in Ferroelectric Materials
• Coexistent topological and chiral phonons in chiral RhGe: An ab initio study
• Femtosecond trimer quench cycled at megahertz rates in the unconventional charge-density wave material $1\text{T’}-{\text{TaTe}}_2$
• Spin-lattice couplings in $3d$ ferromagnets: analysis from first-principles
• Ultrafast pseudomagnetic fields from electron-nuclear quantum geometry
• Spin-spin interaction mediated by chiral phonons
• Spin-phonon dispersion in magnetic materials
• Ultrafast chiral precession of spin and orbital angular momentum induced by circularly polarized laser pulse
• A spin-rotation mechanism of Einstein-de Haas effect based on a ferromagnetic disk
• Einstein-de Haas effect: a bridge linking mechanics, magnetism, and topology
• Generation of ultrashort ion pulses from ultrafast electron-stimulated desorption
• Mechanical resonant sensing of spin texture dynamics in a two-dimensional antiferromagnet
• Cavity-assisted magnetization switching in a quantum spin-phonon chain
• Ultrafast switching of photoinduced phonon chirality in the antiferrochiral BPO${}_4$ crystal
• Catalogue of chiral phonon materials
• Anomalous phonon magnetic moments
• Ultrafast Entropy Production in Non-Equilibrium Magnets
• Laser-induced forces on atoms during ultrafast demagnetization
• Ultrafast Electron Diffraction: Visualizing Dynamic States of Matter
• Dynamical Orbital Angular Momentum Induced by Circularly Polarized Phonons
• Shot-to-shot acquisition ultrafast electron diffraction
• Observation of angular momentum transfer among crystal lattice modes
• Inelastic Neutron Scattering for Direct Detection of Chiral Phonons
• Revealing domain wall stability during ultrafast demagnetization
• How chiral vibrations drive molecular rotation
• Interplay of electron-magnon scattering and spin-orbit induced electronic spin-flip scattering in a two-band Stoner model
• Chiral Phonons Arising From Chirality-Selective Magnon-Phonon Coupling
• Quality of Helicity-Dependent Magnetization Switching by Phonons
• D-Wave Phonon Angular Momentum Texture in Altermagnets by Magnon-Phonon Hybridization
• Ultrafast magnetic moment transfer and bandgap renormalization in monolayer FeCl${}_2$
• Prospects for Direct Electron Detectors in Ultrafast Electron Diffraction and Scattering Experiments
• Electronic mechanism of sub-100-fs demagnetization induced by a femtosecond light pulse
• Mode-Dependent Phonon Relaxation in fcc Ni: Insights from Molecular Dynamics Simulations with Frozen-Trajectory Excitations