# Terahertz-driven Local Dipolar Correlation in a Quantum Paraelectric

## TL;DR

This study investigates how intense terahertz pulses can induce transient local dipolar correlations in quantum paraelectric KTaO₃, revealing long-lived relaxation phenomena linked to defect-induced local polar structures rather than a global ferroelectric phase.

## Contribution

The paper demonstrates that intense THz excitation induces local dipolar correlations without establishing a global ferroelectric phase in KTaO₃, highlighting the role of defect-induced local polar structures.

## Key findings

- Long-lived SHG relaxation up to 20 ps at 10 K.
- Intense THz pulses do not induce global ferroelectricity.
- Local dipolar correlations are driven by defect-induced structures.

## Abstract

Light-induced ferroelectricity in quantum paraelectrics is a new avenue of achieving dynamic stabilization of hidden orders in quantum materials. In this work, we explore the possibility of driving transient ferroelectric phase in the quantum paraelectric KTaO$_3$ via intense THz excitation of the soft mode. We observe a long-lived relaxation in the THz-driven second harmonic generation signal (SHG) that lasts up to 20 ps at 10 K which may be attributed to light-induced ferroelectricity. Through analyzing the THz-induced coherent soft-mode oscillation and finding its hardening with fluence well described by a single well potential, we demonstrate intense THz pulses up to 500 kV/cm cannot drive a global ferroelectric phase in KTaO$_3$. Instead, we find the unusual long-lived relaxation of SHG comes from a THz-driven moderate dipolar correlation between the defect-induced local polar structures. We discuss the impact of our findings on current investigations of the THz-induced ferroelectric phase in quantum paraelectrics.