Terahertz field–induced ferroelectricity in quantum paraelectric SrTiO ₃

TLDR

Hidden phases are metastable collective states not found on equilibrium phase diagrams, offering exotic properties that could enable novel functionality, though their discovery remains in early stages. Intense terahertz electric fields trigger an ultrafast transition to a hidden ferroelectric phase in SrTiO₃, lowering crystal symmetry, altering phonon spectra, and coherently steering ions into a new crystalline arrangement within a single cycle.

Abstract

"Hidden phases" are metastable collective states of matter that are typically not accessible on equilibrium phase diagrams. These phases can host exotic properties in otherwise conventional materials and hence may enable novel functionality and applications, but their discovery and access are still in early stages. Using intense terahertz electric field excitation, we show that an ultrafast phase transition into a hidden ferroelectric phase can be dynamically induced in the quantum paraelectric SrTiO$_3$. The induced lowering in crystal symmetry yields dramatic changes in the phonon excitation spectra. Our results demonstrate collective coherent control over material structure, in which a single-cycle field drives ions along the microscopic pathway leading directly to their locations in a new crystalline phase on an ultrafast timescale.