Ultrafast manipulation of multiferroic BiFeO₃ through light-driven phonons.

Manipulating coupled orderings by external fields or exploring methodologies to achieve ultrafast control of ferroic orderings have driven significant research activities for understanding the physics of multiferroicity. BiFeO₃ shows strong couplings of the lattice structure, electronic and magnetic properties to external fields, which make it appealing for potential applications to encode and access information using a multiferroic bit.

Nonlinear phononics is an emerging approach, in which intense mid-infrared or terahertz laser pulses are used to resonantly excite optical phonons. The high-peak electric fields drive phonon oscillations to large amplitudes. This leads to quasistatic lattice distortion due to strong anharmonic couplings between phonons. The lattice deformation modifies the microscopic Hamiltonian of the system on average, which provides a unique platform to engineer novel functionalities which may not exist in equilibrium, and to achieve selective control of quantum phases such as ferroelectric polarization and magnetic orderings. In this talk, I will present our recent results on the ultrafast manipulation of multiferroic BiFeO₃ by nonlinear phononics.