Vibrational and magnetic spectroscopies at nano-scale

Project title: Vibrational and magnetic spectroscopies at nano-scale
Main applicant: Jan Rusz, Materials Theory
Grant amount: SEK 4 344 000 for the period 2026-2029

In solid state physics, transmission electron microscope is a unique tool allowing to study materials down to atomic scale lateral resolution, while providing information from the interior of the sample. In the last two decades there were significant improvements to the microscope hardware, notably the correction of aberrations of the electron optics, efficient electron beam monochromation and direct electron detection. Monochromated electron beams with dispersion lower than 5 meV can be used to study vibrational properties. In combination with aberration correction that can be done at atomic scale as well. Direct electron detectors provide signal to noise ratios vastly improved over the previous generation detectors. Recently it became possible to reach low temperatures, while – importantly – maintaining the atomic spatial resolution and/or the beam monochromation. These new possibilities call for advances in theory and simulations, both to predict results of experiments and to interpret them. We have recently developed a new theoretical framework, which is both versatile and efficient, and allows to describe phonon and magnon spectroscopy for extended structure models, including models with defects. Recent advances in machine-learned foundational models of interatomic potentials provide flexibility concerning the structure models, as well as access to temperature dependence. We will develop the technique further and apply it to design innovative nano-scale experiments.