Events on Thursday, November 21st, 2024
- R. G. Herb Condensed Matter Seminar
- Pressure and Strain Control of Multiferroic Order in NiI2
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Shua Sanchez, MIT
- Abstract: Multiferroic materials exhibit a linear coupling between simultaneous magnetic and
ferroelectric orders, a rare and unexpected phenomenon. These intriguing materials have attracted
great interest as a platform for energy-efficient computing by using electric fields to control magnetic
states. The van der Waals material NiI2 has been identified as the first multiferroic material in the 2D
limit. Here, a magnetic spin spiral forms between Ni atoms, which breaks inversion symmetry and
induces a ferroelectric polarization. These electronic orders also break the rotational symmetry of the
lattice, enabling structural tuning parameters to directly couple to them. In this talk, I will discuss
pressure and strain tuning measurements of NiI2 which demonstrate the high degree of tunability of
this system, as characterized by x-ray, Raman, and polarimetry measurements. We observe that
transition temperatures can be strongly enhanced by pressure. Further, strain-tuning is shown to control
the polarization direction of the electronic orders. These results present a path forward for structural
custom tuning of multiferroics to realize the goal of ultrafast state switching. - Host: Victor Brar
- Astronomy Colloquium
- Watch Giant Worlds Form and Grow — A Direct Imaging Perspective
- Time: 3:30 pm - 4:30 pm
- Place: 4421 Sterling Hall
- Speaker: Yifan Zhou, University of Virginia
- Abstract: Recent advances have greatly enhanced our understanding of gas giant planet formation and evolution, with discoveries spanning the onset of formation in protoplanetary disks, direct detections of gas accretion, and constraints on the thermal, dynamical, and atmospheric evolution of gas giants. These findings provide crucial insights into the mechanisms underlying the formation of giant planets and the ways these planets impact the formation environment and the broader planetary systems.
This talk will review key direct imaging observations of young gas giant systems, focusing on the identification of protoplanets, the monitoring of accretion onto young planets, and the empirical constraints of the thermal and angular momentum properties of giant planets. Using the PDS 70 system, the only known planetary systems with two actively accreting planets, as a case study, I will illustrate how time-domain, high-contrast imaging can reveal critical details of gas giant formation. I will also highlight ongoing and upcoming James Webb Space Telescope programs that promise transformative insights into the mass growth and early evolution of giant planets. - Host: Melinda Soares-Furtado