Photoinduced dynamics of electronic, structural and magnetic order in quantum materials

Quarta-feira, 19 de Janeiro de 2022 das 16:00 às 18:00
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Quantum materials exhibit a variety of different phases that arise from the competition between different degrees of freedom – electronic, stru­­ctural, spin and orbital. Ultrafast techniques enable a selective investigation of the dynamical response of these different subsystems through a careful choice of pump and probe characteristics.

I will present results of studies in different quantum materials using ultrafast pulses in the optical, THz and x-ray frequency ranges.

TbMnO3 is a prototypical multiferroic, where ferroelectric polarization arises from a cycloidal magnetic order below 27 K. The prospect of electric field control of magnetization dynamics makes multiferroic systems extremely appealing, in particular in the context of ultrafast magnetic switching. Using ultrafast x-ray pulses we have investigated the magnetic order and structural dynamics in TbMnO_3 following optical and THz excitation, shedding light onto the demagnetization pathways in this system.

Mott insulators are archetypal examples of quantum materials, which have generated strong interest due in part to the insulator-to-metal transition that some exhibit when the balance between on-site Coulomb repulsion and hopping is overturned. Some Mott insulators exhibit an abrupt drop in resistivity under the application of electric fields with durations of a few tens of microseconds, with typical threshold fields on the order of 1-10 kV/cm. Quasi-dc electric fields well in excess of 1 – 10 kV/cm can currently be generated with ultrashort pulses in the low frequency or THz range, which enables the investigation of the sub-picosecond dynamics of the electric field driven Mott transition. I will present our results on THz driven dynamics in GaTa_4Se_8, a Mott insulator which exhibits clear electrical Mott transitions.

Short Bio:
Elsa Abreu is a Senior Research Assistant in the Physics Department of ETH Zürich. In 2018 she was awarded a four-year Ambizione Grant from the Swiss National Science Foundation for her project on "Exploring superconductivity pathways in low-dimensional spin-ladder and spin-chain compounds", and has since then been leading a team as a part of the Ultrafast Dynamics Group.

She obtained her BSc in Physics from the Instituto Superior Técnico and her MSc at Instituto Superior Técnico and Uppsala University, Sweden. In 2014 she graduated with her PhD in Physics from Boston University, MA, USA, and then moved to Switzerland to work as a postdoctoral fellow at ETH Zürich.