title: Chiral phonons at high-symmetry points in monolayer hexagonal lattices.
abstract: In monolayer hexagonal lattices, the intravalley and intervalley scattering of electrons can involve chiral phonons at Brillouin-zone center and corners, respectively. At these high-symmetry points, there is a threefold rotational symmetry endowing phonon eigenmodes with a quantized pseudoangular momentum, which includes orbital and spin parts. Conservation of pseudoangular momentum yields selection rules for intravalley and intervalley scattering of electrons by phonons. Concrete predictions of helicity-resolved optical phenomena are made on monolayer molybdenum disulfide. The chiral phonons at Brillouin-zone corners excited by polarized photons can be detected by a valley phonon Hall effect. The chiral phonons, together with phonon circular polarization, phonon pseudoangular momentum, selection rules, and valley phonon Hall effect will extend the basis for valley-based electronics and phononics applications in the future.
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.|Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing 210023, China.
authors.forename: Lifa
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA.|International Center for Quantum Materials, Peking University, Beijing 100871, China.
authors.forename: Qian
authors.initials: Q
authors.lastname: Niu