Phonon Chirality Induced by Vibronic-Orbital Coupling

TL;DR

This paper demonstrates phonon chirality induced by vibronic-orbital coupling, revealing angular momentum transfer in vibronic bound states, which impacts the engineering of topological phonon band structures.

Contribution

It provides the first experimental observation of angular momentum transfer between phonons and orbital states in vibronic bound states.

Findings

Angular momentum transfer of ±1ħ observed

Phonon chirality linked to vibronic coupling

Implications for topological phonon engineering

Abstract

The notion that phonons can carry pseudo-angular momentum has become popular in the last decade, with recent research efforts highlighting phonon chirality, Berry curvature of phonon band structure, and the phonon Hall effect. When a phonon is resonantly coupled to a crystal electric field excitation, a so-called vibronic bound state forms. Here, we observe angular momentum transfer of $\delta$Jz = $\pm$1$\hbar$ between phonons and an orbital state in a vibronic bound state of a candidate quantum spin liquid. This observation has profound implications for the engineering of phonon band structure topology through chiral quasiparticle interactions.