Simulating terahertz field-induced ferroelectricity in quantum paraelectric SrTiO$_3$

TL;DR

This study uses first-principles simulations to explore how terahertz light can induce a ferroelectric phase transition in SrTiO$_3$, revealing microscopic mechanisms behind this quantum phase change.

Contribution

It provides a detailed theoretical analysis of the light-induced ferroelectric transition in SrTiO$_3$, linking experimental observations with microscopic lattice dynamics.

Findings

Light induces ferroelectricity via lattice state mixing.

Second harmonic generation signals indicate ferroelectric phase.

Transition is unique to quantum paraelectric phase.

Abstract

Recent experiments have demonstrated that light can induce a transition from the quantum paraelectric to the ferroelectric phase of SrTiO$_3$. Here, we investigate this terahertz field-induced ferroelectric phase transition by solving the time-dependent lattice Schr\"odinger equation based on first-principles calculations. We find that ferroelectricity originates from a light-induced mixing between ground and first excited lattice states in the quantum paraelectric phase. In agreement with the experimental findings, our study shows that the non-oscillatory second harmonic generation signal can be evidence of ferroelectricity in SrTiO$_3$. We reveal the microscopic details of this exotic phase transition and highlight that this phenomenon is a unique behavior of the quantum paraelectric phase.