Spacetime representation of topological phononics. (2nd May 2018)

• Record Type: Journal Article
• Authors: Deymier, Pierre A; Runge, Keith; Lucas, Pierre; Vasseur, Jérôme O
• Is Part Of: New journal of physics. Volume 20:Number 5(2018:May)
• Publication Date: 2018-05-02
• Subjects: topological phononics -- ghost phonons -- twistor theory -- Dirac phonons -- spacetime; Physics -- Periodicals; Physics; Periodicals; 530.05
• DOI: 10.1088/1367-2630/aaba18
• Languages: English
• ISSNs: 1367-2630

Abstract

Abstract: Non-conventional topology of elastic waves arises from breaking symmetry of phononic structures either intrinsically through internal resonances or extrinsically via application of external stimuli. We develop a spacetime representation based on twistor theory of an intrinsic topological elastic structure composed of a harmonic chain attached to a rigid substrate. Elastic waves in this structure obey the Klein–Gordon and Dirac equations and possesses spinorial character. We demonstrate the mapping between straight line trajectories of these elastic waves in spacetime and the twistor complex space. The twistor representation of these Dirac phonons is related to their topological and fermion-like properties. The second topological phononic structure is an extrinsic structure composed of a one-dimensional elastic medium subjected to a moving superlattice. We report an analogy between the elastic behavior of this time-dependent superlattice, the scalar quantum field theory and general relativity of two types of exotic particle excitations, namely temporal Dirac phonons and temporal ghost (tachyonic) phonons. These phonons live on separate sides of a two-dimensional frequency space and are delimited by ghost lines reminiscent of the conventional light cone. Both phonon types exhibit spinorial amplitudes that can be measured by mapping the particle behavior to the band structure of elastic waves.