Seminars And Colloquia This Week

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Meeting ID: 981 6665 1049
Password: 726235

Monday, March 8, 2021
1:00 PM
Online, Room Zoom

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"Recent developments in the post-Minkowskian approach to the spinning black hole binary problem"

Justin Vines , Max Planck Institute for Gravitational Physics (Albert Einstein Institute)
[Host: Alexander Grant]

The detection and analysis of gravitational wave signals from coalescing binary systems crucially relies on analytic perturbative approaches to the two-body problem in general relativity (as well as on numerical approaches).  While the post-Newtonian (weak-field and slow-motion) approximation is most directly relevant to observations by LIGO et al., recent developments have revived interest in the more inclusive post-Minkowskian (weak-field but arbitrary-speed) approximation -- particularly in relation to highly advanced techniques developed by particle physicists for computing relativistic quantum scattering amplitudes and associated classical observables.  This interplay between high-energy quantum physics and gravitational-wave science has led to several new results and useful insights, particularly regarding relationships between complimentary approximation schemes; this importantly also includes the "self-force" or "post-test-body" approach, treating small mass ratios but arbitrary field strengths and speeds.  We will review some of these developments, focusing on the post-Minkowskian treatment of the spinning black hole binary problem.

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Thursday, March 11, 2021
3:30 PM
Online, Room via Zoom
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"Ferrimagnetic materials for room temperature small skyrmions"

Wei Zhou , University of Virginia - Department of Physics
[Host: Joe Poon]

The magnetic skyrmions are topologically protected spin configuration, which stabilized by Dzyaloshinskii-Moriya interaction (DMI). Due to skyrmions’ ability to be small, stable, and controllable by electric current [1], they have considerable potential for high-density data storage applications. It is theoretically predicted that ferrimagnetic materials prefer holding small skyrmions at room temperature (RT) [2,3]. 10-15nm ferrimagnetic CoGd heterostructures and 10-15nm ferrimagnetic Mn4N heterostructures were fabricated by magnetron sputtering for holding small skyrmions at RT. Magnetic force microscope images show skyrmions. A designed compound layer is capping on the top of the magnetic layer to adjust the interfacial DMI, thus tune the size of skyrmions. The micromagnetic simulation was performed to study the effect of DMI on the size of skyrmions Mn4N.


[1] Fert, A., et al. Magnetic skyrmions: advances in physics and potential applications. Nat Rev Mater 2, 17031 (2017).
[2] Büttner, F., et al. Theory of isolated magnetic skyrmions: From fundamentals to room temperature applications. Sci Rep 8, 4464 (2018).
[3] C.T. Ma., et al. Robust Formation of Ultrasmall Room-Temperature Neél Skyrmions in Amorphous Ferrimagnets from Atomistic Simulations. Sci Rep 9, 9964 (2019).

To add a speaker, send an email to phys-speakers@Virginia.EDU. Please include the seminar type (e.g. Seminars and Colloquia), date, name of the speaker, title of talk, and an abstract (if available).