Magneto-Optics and Non-Linear Spectroscopy Group: Research Topics

We aim at discovering and developing new mechanisms for manipulating the optical and magnetic properties of matter. This project started around 2010. As of March 2018, the manipulation of antiferromagnets by an external signal was an emerging field with rich new physics and high potential for revolutionary technological applications, as described then in an editorial of the prestigious Nature Physics journal.

Fast magnetic state manipulation requires access to the ultra-short (sub-nanosecond) time scale, because this is the characteristic time scale involved. For example, the precession period of an electron spin in a magnetic field of 1 Tesla is 35.7 picoseconds (1 picosecond=1 trillionth of a second). We use picosecond and femtosecond light pulses to induce changes in the magnetic and optical properties of solids, and to monitor these properties as they evolve in time, with femtosecond resolution. Our experiments are firmly backed by theoretical models for light-matter interaction and many-body systems, which we develop using quantum mechanics and statistical physics. We focus, in particular, on yet unexplored mechanisms by which illumination influences magnetic order. Recently, we obtained surprising and spectacular results in antiferromagnetic EuSe, where using light we converted a zero-magnetization state into a saturated ferromagnet in 50 trillionths of a second. We demonstrated that in EuSe the absorption of a single photon flips the spin of nearly six thousand electrons. Our result paves a novel path for ultrafast switching of the magnetic state of matter using few photons (free access preprint here, full publication here). Work funded by FAPESP, CNPq, NAP/USP, CAPES.

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