Mirror-symmetry-induced pseudospin filtering of phonons in graphene nanoribbons

Abstract

Unlike electrons, phonons do not have the charge and spin degrees of freedom. Consequently, it is a big challenge for the control of phonon currents and the design of quantum phonon devices due to the lack of versatile degrees of freedom. In this work, we show that phonon bands of mirror-symmetric materials can be labeled by parities, which can act as a pseudospin of phonons. As a proof-of-concept, we show that perfect pseudospin filtering can be realized using mirror-symmetric graphene-nanoribbon heterojunctions. In addition, we show that the filtering takes place within a remarkably short length scale of just 3 nanometers. Our work reveals an intriguing new facet of phonon behavior and also underscores the immense potential of utilizing phonons as information carriers.

Keywords

• pseudospin
• phonons
• graphene
• mirror symmetry
• parity