Condense Matter Physics Seminar: Incommensurate magnetism mediated by Weyl fermions in NdAlSi, by Dr. Jonathan Gaudet of NIST

March 22, 2021 @ 4:00 pm – 5:00 pm America/New York Timezone

Title: Incommensurate magnetism mediated by Weyl fermions in NdAlSi

Speaker: Dr. Jonathan Gaudet , NIST

Time: March 22, 2021 04:00 PM Eastern Time (US and Canada)

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Abstract: Emergent relativistic quasiparticles in Weyl semimetals are the source of exotic electronic properties such as surface Fermi arcs, the anomalous Hall effect, and negative magnetoresistance, all observed in real materials. Whereas these phenomena highlight the effect of Weyl fermions on the electronic transport properties, less is known about what collective phenomena they may support. In this talk, I will report a new Weyl semimetal, NdAlSi that offers an example. Using neutron diffraction, a long-wavelength magnetic order in NdAlSi whose periodicity is linked to the nesting vector between two topologically non-trivial Fermi pockets was observed, and characterized using density functional theory and quantum oscillation measurements. This work provides a rare example of Weyl fermions driving collective magnetism.


Dr. Gaudet did his PhD under the supervision of Bruce Gaulin at McMaster University in Hamilton, Canada (2014-2018). There he studied neutron scattering of frustrated rare-earth pyrochlores. He then moved to do a postdoc with Collin Boholm at Johns Hopkins University (2018-2021) to study magnetic topological materials with neutrons. Very recently (March 1st), Dr. Gaudet moved to the NIST Center for Neutron Research in Gaithersburg, Maryland to start a position as Research scientist.