Chiral phonons probed by X rays

TL;DR

This paper provides experimental evidence of chiral phonons in quartz using resonant inelastic X-ray scattering with circularly polarized X rays, revealing their dispersion and opening new avenues in condensed matter physics.

Contribution

It introduces a novel experimental method to detect and analyze chiral phonons, a previously elusive bosonic degree of freedom in condensed matter.

Findings

Circularly polarized X rays couple to chiral phonons at specific reciprocal space points.

Chiral phonons exhibit a distinct dispersion relation in quartz.

The study confirms the existence of chiral phonons as a fundamental lattice excitation.

Abstract

The concept of chirality is of great relevance in nature, from chiral molecules such as sugar to parity transformations in particle physics. In condensed matter physics, recent studies have demonstrated chiral fermions and their relevance in emergent phenomena closely related to topology. The experimental verification of chiral phonons (bosons) remains challenging, however, despite their expected strong impact on fundamental physical properties. Here we show experimental proof of chiral phonons using resonant inelastic X-ray scattering with circularly polarized X rays. Using the prototypical chiral material, quartz, we demonstrate that circularly polarized X rays, which are intrinsically chiral, couple to chiral phonons at specific positions in reciprocal space, allowing us to determine the chiral dispersion of the lattice modes. Our experimental proof of chiral phonons demonstrates a new degree of freedom in condensed matter that is both of fundamental importance and opens the door to exploration of novel emergent phenomena based on chiral bosons