Light-Driven Transitions in Quantum Paraelectrics

TL;DR

This paper investigates how strong light pulses can induce phase transitions and complex behaviors in quantum paraelectrics like SrTiO$_3$, including polar ordering, two-step transitions, and chaos, with quantum effects modifying classical predictions.

Contribution

It introduces a systematic approach to analyze driven phonon systems near phase transitions, incorporating quantum corrections to classical dynamics.

Findings

Light-induced polar phases depend on light polarization.

Two-step transitions occur at specific fluence profiles.

Quantum fluctuations shift the critical pump fluence.

Abstract

Motivated by recent experiments on pump-induced polar ordering in the quantum paraelectric SrTiO$_3$, we study a driven phonon system close to a second order phase transition. Analyzing its classical dynamics, we find that sufficiently strong driving leads to transitions into polar phases whose structures, determined by the light polarization, are not all accessible in equilibrium. In addition, for certain intensity profiles we demonstrate the possibility of two-step transitions as a function of fluence. For even stronger field intensities, the possibility of period-doubling and chaotic behavior is demonstrated. Finally we develop a generalized formalism that allows us to consider quantum corrections to the classical dynamics in a systematic fashion. We predict a shift in the critical pump fluence due to quantum fluctuations with a characteristic dependence on the fluence increase rate, which can be observed in experiments.