Observation of angular momentum transfer among crystal lattice modes

Abstract

Transfer of energy and linear momentum between lattice vibrations via anharmonic coupling is an important concept in solid-state physics. However, it remains difficult to directly observe how angular momentum is exchanged and conserved among lattice modes, even though these processes are thought to play an important role in achieving magnetization equilibrium and in spin relaxation effects like the Einstein-de Haas effect. Here, we demonstrate and coherently control angular momentum transfer between two lattice modes using the inverse process of anharmonic decay. The observed rotational phonon-phonon Umklapp scattering enforces the conservation of quantized crystal angular momentum, as dictated by the crystal's discrete rotational symmetry. We thereby experimentally confirm the fundamental analogy between linear and angular momentum conservation in solids. Moreover, we establish axial nonlinear phononics towards ultrafast control of material properties.

57 pages , 18 figures (includes Extended Figures and Supplementary Information)

References in corpus (13)

• Giant thermal Hall conductivity from neutral excitations in the pseudogap phase of cuprates
• 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
• Phonon driven Floquet matter
• Phononic Switching of Magnetization by the Ultrafast Barnett Effect
• Catalogue of topological phonon materials
• Nonlinear THz Control of the Lead Halide Perovskite Lattice
• Two-dimensional THz spectroscopy of nonlinear phononics in the topological insulator ${\mathrm{MnBi}}_2{\mathrm{Te}}_4$
• Observation of Phonon Angular Momentum
• Phonon Inverse Faraday effect from electron-phonon coupling
• Coherent control of the translational and point group symmetries of crystals with light
• Generation of Phonons with Angular Momentum During Ultrafast Demagnetization