Light-induced modulation of electrical, optical, and thermodynamic properties via nonlinear phononics in perovskite KTaO₃

Strong long-wavelength laser pulses enable direct manipulation of atomic lattices for engineering novel quantum states in complex materials. Nonlinear coupling between two infrared-active phonon modes (TO₁ and TO₂), induced by intense terahertz light fields, significantly enhances the amplitude of the TO₁ mode and facilitates ultrafast control of transient structural distortions. This light-induced distortion reduces the lattice thermal conductivity from 8.1 W⋅m⁻¹⋅K⁻¹ to 3.0 W⋅m⁻¹⋅K⁻¹. The reduction originates from the nonlinear coupling, which enhances anharmonic interactions in the lattice potential energy and substantially shortens the phonon lifetime (τ). This work demonstrates a strategy applicable to other perovskite materials and provides a framework for investigating light-induced electrical, optical, and thermodynamic phase transitions.