Condensed-Matter Physics & Materials Science Seminar

Electron holography has the potential to achieve single-spin and single-charge sensitivity in measuring nanoscale magnetic and electric fields. This extreme sensitivity is needed to solve outstanding challenges in condensed matter physics and materials sciences, such as, just to name a few: i) understanding the origin of exchange bias, ii) solving the spin structure of various magnetic interfaces, iii) quantifying charge transfer in functional nanomaterials, iv) explaining the Berriman effect. To develop quantitative electron holography along these lines, I introduced a paradigmatic shift in the way holographic phase images are processed and analyzed: from a model-based approach where charge and spin distributions are statistically inferred on the basis of image simulations, to a set of new algorithms that gives us access to field sources directly from special operations on the phase images, without the need for a-priori knowledge, or approximate mathematical representations of the sample under scrutiny. Two examples will be discussed during this presentation: counting electrons along a biassed carbon nanotube bundle, and counting Bohr magnetons in small magnetic nanoparticles.