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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 21: Focus Session: SrTiO₃: A Versatile Material from Bulk Quantum Paraelectric to 2D Superconductor (joint session TT/KFM/MA/O)

KFM 21.7: Talk

Thursday, March 21, 2024, 12:30–12:45, H 0104

Dynamics of the critical phonon modes in quantum paraelectric SrTiO₃ — •Shiyu Deng^1,2, Charles S. Haines^1,3, Matthew J. Coak^1,4, Alexandre Ivanov², Andrea Piovano², Andrew R. Wildes², and Siddharth S. Saxena¹ — ¹Cavendish Laboratory, University of Cambridge — ²Institut Laue-Langevin — ³University of East Anglia — ⁴University of Birmingham

The proximity of SrTiO₃ to a ferroelectric quantum critical point (FE QCP) has become a promising new branch of the study of quantum critical phenomena. New forms of quantum order have been reported in SrTiO3 different from the quantum paraelectric state via dielectric measurements.

We report our recently performed triple-axis inelastic neutron scattering experiments on single-crystal SrTiO₃ at the temperature and pressure region of interest. These were the first direct measurements deep into the enigmatic ’quantum polar-acoustic state’ in the vicinity of the FE QCP. Measurements are taken at and around q = 0 in multiple directions in reciprocal space to explore the transverse acoustic and soft optical phonon modes and their hybridization. In addition, we explore how pressure affects the underlying phonon modes in SrTiO₃. Our observations address directly the coupling of the soft optical mode with the acoustic phonons, and its response to external pressure. We believe this could help us understand the importance of anharmonic lattice dynamics and quantum fluctuations in SrTiO₃.

Keywords: inelastic neutron scattering; ferroelectric quantum criticality