Strain tuning of Soft Phonons in Incipient Ferroelectrics

Strontium titanate (SrTiO3, STO), potassium tantalate (KTaO­3, KTO), and lead telluride (PbTe) exhibit giant ferroelectric fluctuations at low temperatures that are associated with a soft polar transverse optical (TO) phonon mode [1-3]. It has been proposed that this phonon plays a central role in the superconducting pairing mechanism in this class of materials [4], and it is therefore important to understand its properties. Strain has been shown to be an effective tuning parameter with which to push STO into the ferroelectric phase [5], yet such experiments have only been feasible with experimental probes that do not require sizable samples, such as inelastic neutron scattering. Here we report on our inelastic neutron scattering investigation of the soft phonon modes in STO, KTO, and PbTe under in situ uniaxial stress utilizing a newly developed high-force pneumatic strain cell.

References

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