Chiral Phonons at High-Symmetry Points in Monolayer Hexagonal Lattices

Lifa Zhang and Qian Niu

Phys. Rev. Lett. 115, 115502 – Published 11 September 2015

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.

Received 9 February 2015

DOI:https://doi.org/10.1103/PhysRevLett.115.115502

Authors & Affiliations

Lifa Zhang^1,2 and Qian Niu^1,3

¹Department of Physics, The University of Texas at Austin, Austin, Texas 78712, USA
²Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing 210023, China
³International Center for Quantum Materials, Peking University, Beijing 100871, China