Phonon Magnetochiral Effect

Area of Science:

• Condensed Matter Physics
• Solid-State Acoustics
• Magnetism

Background:

• The magnetochiral effect (MCE) describes nonreciprocal wave propagation influenced by magnetic fields and material chirality.
• Understanding MCE in acoustic systems is crucial for exploring novel phononic phenomena.

Purpose of the Study:

• To experimentally demonstrate the magnetochiral effect (MCE) of phonons.
• To investigate the influence of magnetic fields and crystal chirality on acoustic wave propagation.
• To elucidate the underlying mechanism responsible for the observed MCE.

Main Methods:

• High-resolution ultrasound experiments were conducted.
• Measurements of sound velocity were performed under varying magnetic field orientations.
• Analysis focused on the nonreciprocity of acoustic propagation in chiral magnetic materials.

Main Results:

• The magnetochiral effect (MCE) of phonons was successfully demonstrated in the chiral-lattice ferrimagnet Cu_{2}OSeO_{3}.
• A distinct difference in sound velocity was observed for parallel and antiparallel acoustic propagation relative to the external magnetic field.
• The sign of the nonreciprocity was found to be dependent on the crystal's chirality, aligning with MCE selection rules.
• Enhanced nonreciprocity was noted below the magnetic ordering temperature and at higher ultrasound frequencies.

Conclusions:

• The study confirms the existence of the magnetochiral effect for phonons in magnetic materials.
• A magnon-phonon hybridization mechanism is proposed and quantitatively explains the observed MCE, particularly its temperature and frequency dependence.
• Findings provide insights into the interplay between magnetism, crystal structure, and acoustic properties.