UPSHIFT · Ultrafast Phonon-Driven Switching in Multiferroic Materials

Manipulating the magnetic state of media with minimal energy and in the shortest possible time is a fundamental challenge in physics, as faster switching typically requires higher energy. The challenge is increasingly urgent, as the rapid rise of the Internet of Things and Artificial Intelligence has surged the energy demand of data centers, making them a significant source of global carbon emissions. To enable a sustainable digital future, we need computing devices that operate in less than a trillionth of a second while consuming below a femtojoule per bit. Controlling magnetization with electric fields in multiferroic materials, at energy costs in the attojoule range, offers a promising route. However, under ultrafast operation, the energy exchange between spins, electric polarization, and phonons undergoes dramatic changes. The lack of effective control strategies leads to heat losses and limits switching efficiency.UPSHIFT aims to establish new principles and benchmarks for ultrafast, energy-efficient switching of multiferroics. I will use intense THz electric fields (MV-GV/cm) to coherently excite lattice vibrations at selected phonon frequencies in model multiferroics (BiFeO₃ and NiI2). This approach will induce controlled, non-thermal lattice deformation, allowing for the steering of spin-phonon couplings at sub-picosecond timescales. Using a second excitation pulse, I will map the regulation of the energy flow among the spin, lattice, and electronic subsystems and quantify its impact on switching dynamics, threshold energy, and speed. Studying materials with contrasting coupling regimes and dimensionalities will uncover both universal principles and material-specific pathways for ultrafast, low-energy switching. The proposal will benefit from the unique HFML-FELIX facility and tabletop femtosecond laser sources available at Radboud University, enabling the establishment of new benchmarks for next-generation, energy-efficient devices.