Anharmonic Eigenvectors and Acoustic Phonon Disappearance in Quantum Paraelectric ${\mathrm{SrTiO}}_{3}$

Anharmonic Eigenvectors and Acoustic Phonon Disappearance in Quantum Paraelectric ${SrTiO}_{3}$

Xing He, Dipanshu Bansal, Barry Winn, Songxue Chi, Lynn Boatner, and Olivier Delaire

Phys. Rev. Lett. 124, 145901 – Published 9 April 2020

Abstract

Pronounced anomalies in the ${SrTiO}_{3}$ dynamical structure factor, $S (Q, E)$ , including the disappearance of acoustic phonon branches at low temperatures, were uncovered with inelastic neutron scattering (INS) and simulations. The striking effect reflects anharmonic couplings between acoustic and optic phonons and the incipient ferroelectric instability near the quantum critical point. It is rationalized using a first-principles renormalized anharmonic phonon approach, pointing to nonlinear Ti-O hybridization causing unusual changes in real-space phonon eigenvectors, frequencies, group velocities, and scattering phase space. Our method is general and establishes how $T$ dependences beyond the harmonic regime, assessed by INS mapping of large reciprocal-space volumes, provide real-space insights into anharmonic atomic dynamics near phase transitions.

Received 10 September 2019
Revised 19 January 2020
Accepted 16 March 2020

DOI:https://doi.org/10.1103/PhysRevLett.124.145901

Physics Subject Headings (PhySH)

Anharmonic lattice dynamics Antiferroelectricity Dynamical phase transitions Ferroelectricity Heat transfer Lattice thermal conductivity Phonons Quantum criticality

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Xing He ¹, Dipanshu Bansal ², Barry Winn³, Songxue Chi ³, Lynn Boatner⁴, and Olivier Delaire ^1,5,6,*

¹Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina 27708, USA
²Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai, Maharashtra 400076, India
³Neutron Scattering Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
⁴Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
⁵Department of Physics, Duke University, Durham, North Carolina 27708, USA
⁶Department of Chemistry, Duke University, Durham, North Carolina 27708, USA