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Interplay between phonon chirality and electronic topology

  • Phonons are important collective excitations in materials. Typically, they do not respond to magnetic field and do not carry a magnetic moment (chirality).
  • Phonon chirality can be induced via two mechanisms (i) adiabatic evolution with electronic states that break time-reversal symmetry (e.g. magnetism) and (ii) phonon induced mixing of different electronic energy levels.
  • Chiral phonons observed in topological crystalline insulator Pb1-xSnxTe using THz magneto-spectroscopy
  • Phonon magnetic moment changed sign across topological phase transition and was two orders of magnitude higher in the topological phase
  • Connection between chiral phonons and electronic topology opens new ways to control matter