Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Spontaneous Decay of a Soft Optical Phonon in the Relaxor Ferroelectric PbMg1/3Nb2/3O3



C. Stock, Peter M. Gehring, R. A. Ewings, Guangyong Xu, Jiefang Li, Dwight Viehland, Haosu Luo


We report the spontaneous decay of a soft, optical phonon in a solid. Using neutron spectroscopy, we find that specific phonon lifetimes in the relaxor PbMg1/3Nb2/3O3 are anomalously short within well-defined ranges of energy and momentum. This behavior is independent of ferroelectric order and occurs when the optical phonon with a specific energy and momentum can kinematically decay into two acoustic phonons with lower phase velocity.We interpret the well-known relaxor "waterfall" effect as a form of quasiparticle decay analogous to that previously reported in quantum spin liquids and quantum fluids.
Physical Review Materials


Lattice dynamics, phonons, quasiparticle decay, anharmonicity, relaxors, PMN, perovskite, neutron scattering


Stock, C. , Gehring, P. , Ewings, R. , Xu, G. , Li, J. , Viehland, D. and Luo, H. (2018), Spontaneous Decay of a Soft Optical Phonon in the Relaxor Ferroelectric PbMg<sub>1/3</sub>Nb<sub>2/3</sub>O<sub>3</sub>, Physical Review Materials, [online], (Accessed April 15, 2024)
Created February 12, 2018, Updated October 12, 2021