Terahertz-Field-Induced Ferroelectricity in Quantum Paraelectric SrTiO$_3$

TL;DR

This study demonstrates that intense terahertz electric fields can induce a hidden ferroelectric phase in SrTiO$_3$, revealing ultrafast control over material phases and symmetry on a femtosecond timescale.

Contribution

It introduces a method to dynamically access and control hidden phases in quantum paraelectrics using ultrafast terahertz excitation, revealing new pathways for phase manipulation.

Findings

Ultrafast phase transition to a hidden ferroelectric state in SrTiO$_3$

Significant changes in phonon spectra due to symmetry lowering

Single-cycle terahertz fields drive ions to new crystalline positions

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.