Propagation of longitudinal acoustic phonons in ZrTe$_{\boldsymbol{5}}$ exposed to a quantizing magnetic field

TL;DR

This study investigates how longitudinal acoustic phonons propagate in ZrTe$_5$ under a magnetic field, revealing electron-phonon interactions and their impact on sound velocity and attenuation, with theoretical models aligning with experimental data.

Contribution

The paper provides a microscopic analysis of electron-phonon coupling effects on phonon propagation in ZrTe$_5$ under magnetic fields, connecting theory with experimental ultrasound measurements.

Findings

Quantum oscillations in ultrasound measurements linked to electron-phonon coupling.

Sound velocity renormalization and attenuation match theoretical predictions.

Results suggest a metallic Dirac model describes ZrTe$_5$ behavior up to the quantum limit.

Abstract

The compound ZrTe$_5$ has recently been connected to a charge-density-wave (CDW) state with intriguing transport properties. Here, we investigate quantum oscillations in ultrasound measurements that microscopically originate from electron-phonon coupling and analyze how these would be affected by the presence or absence of a CDW. We calculate the phonon self-energy due to electron-phonon coupling, and from there deduce the sound-velocity renormalization and sound attenuation. We find that the theoretical predictions for a metallic Dirac model resemble the experimental data on a quantitative level for magnetic fields up to the quantum-limit regime.