TSAR is focused on mastering topological objects in two main classes of materials i.e. antiferromagnets - AF - and (anti)ferroelectrics- (A)FE. In this first 30 months, experimental and theoretical work have produced results on all fronts. Firstly, a substantial effort on materials has allowed to produce antiferroic films with high reliability. Among the available materials, some show great promise for AF skyrmion generation. In particular, beside the totally optimized synthetic antiferromagnets, strain engineered BiFeO3 can now lead to compounds where the intrinsic cycloidal state is suppressed putting the material at the verge of metastability of individual entities: AF skyrmions. On the electric side, beside the perfectly mastered PbTiO3-based superlattices, huge progress has been made in the growth and understanding of antiferroelectric PbZrO3. Its complex antiferroelectric phase is now well studied and topologically protected ferri-electric entities have been observed. Electric-field and temperature behaviour of the AFE/FE transition have also been clarified by our extensive tools, some of them developed for the TSAR project. On that front, our consortium avails of the state of the art capabilities to image topological entities including NV center magnetometry along with its noise mapping, MFM and PFM microscopies and atomically resolved TEM with operando capabilities. Dynamical measurements at the sub-picosecond timescale have also been designed using optics and will be applied in the second part of the project. Moreover, on the theoretical front, several codes have been developed either on atomistic magnetic/electric calculations, along with phase-field and DFT and a second-principles model has been constructed. Some interesting progress has also been made in the theory for soliton nucleation with OAM light using already built effective Hamiltonian models in Molecular Dynamics simulations using Laguerre-Gauss beams.
Regarding the challenge of writing topological AF entities, light pulses carrying OAM have been optimized and used on Synthetic Antiferromagnets (SAF), and BiFeO3. Skyrmions can now be written with OAM light in SAFs, but the role of AOM is not yet understood.
