Colloquia This Term

Click on the following link to attend the online colloquium:
https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Friday, February 5, 2021
3:30 PM
Physics Building, Room via Zoom
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"A fermionic triangular-lattice quantum gas microscope "


Peter Schauss , University of Virginia - Physics Dept.
[Host: Bob Jones]
ABSTRACT:

Geometrically frustrated many-body systems show many interesting emerging phenomena, ranging from kinetic frustration to exotic spin ordering and chiral spin liquid phases. Ultracold atom systems offer great tunability and flexibility to realize such systems in a wide parameter range of interactions, densities, and spin-imbalance.

In this talk, I will present our recent results on site-resolved imaging of ultracold fermionic lithium atoms on a triangular optical lattice.

Degenerate Fermi gases with about one tenth of the Fermi temperature have been realized within a crossed dipole trap and successfully loaded into a two-dimensional triangular optical lattice. To characterize this lattice, we observed Kapitza-Dirac scattering using a molecular Bose-Einstein condensate. Collecting the emitted photons during Raman sideband cooling in the triangular lattice using a high-resolution microscope objective enabled the high-fidelity imaging of individual fermionic atoms in the lattice with single-site resolution.

The next step will be the realization of a triangular lattice Hubbard model by implementing an additional optical lattice to increase interactions.

This novel experimental platform will allow us to study spin and density correlations in the triangular Hubbard model to explore signatures of frustration and spin-hole bound states and may lead to a direct observation of non-vanishing chiral correlations.

VIDEO:
Click on the following link to attend the online colloquium:
https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Friday, February 12, 2021
2:00 PM
Online, Room via Zoom
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"Complexity of magnetic patterns and self-induced spin-glass state"


Prof. Mikhail Katsnelson , Radboud University of Nijmegen, The Netherlands,
[Host: Dima Pesin]
ABSTRACT:

The origin of complexity remains one of the most important and, at the same time, the most controversial scientific problems. Earlier attempts were based on theory of dynamical systems but did not lead to a satisfactory solution of the problem. I believe that a deeper understanding is possible based on a recent development of statistical physics, combining it with relevant ideas from evolutionary biology and machine learning.

Using patterns in magnetic materials as the main example, I discuss some general problems such as (a) a formal definition of pattern complexity [1]; (b) self-induced spin glassiness due to competing interactions as a way to interpret chaotic patterns [2]; (c) multi-well states intermediate between glasses and ordinary ordered states and their relevance for the problem of long-term memory in complicated systems [3]; and (d) complexity of frustrated quantum spin systems [4]. I will also review a very recent experimental observation of self-induced spin-glass state in elemental neodymium [5].

[1] A. A. Bagrov, I. A. Iakovlev, A. A. Iliasov, M. I. Katsnelson, and V. V. Mazurenko, Multi-scale structural complexity of natural patterns, PNAS 117, 30241 (2020).
[2] A. Principi and M. I. Katsnelson, Spin glasses in ferromagnetic thin films, Phys. Rev. B 93, 054410 (2016); Self-induced glassiness and pattern formation in spin systems due to long-range interactions, Phys. Rev. Lett. 117, 137201 (2016).
[3] A. Kolmus, M. I. Katsnelson, A. A. Khajetoorians, and H. J. Kappen, Atom-by-atom construction of attractors in a tunable finite size spin array, New J. Phys. 22, 023038 (2020).
[4] T. Westerhout, N. Astrakhantsev, K. S. Tikhonov, M. I. Katsnelson, and A. A. Bagrov, Generalization properties of neural network approximations to frustrated magnet ground states, Nature Commun. 11, 1 (2020).
[5] U. Kamber et al, Self-induced spin glass state in elemental and crystalline neodymium, Science 368, eaay6757 (2020).
VIDEO:
Colloquium
Friday, February 19, 2021
3:30 PM
Online, Room via Zoom
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RESERVED
Colloquium
Friday, February 26, 2021
3:30 PM
Physics Building, Room TBA
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Colloquium
Friday, March 5, 2021
3:30 PM
Physics Building, Room TBA
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RESERVED
Colloquium
Friday, March 12, 2021
3:30 PM
Physics Building, Room Online
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RESERVED
Colloquium
Friday, March 19, 2021
3:30 PM
Physics Building, Room TBA
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Colloquium
Friday, March 26, 2021
3:30 PM
Physics Building, Room TBA
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Colloquium
Friday, April 2, 2021
3:30 PM
Physics Building, Room TBA
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Colloquium
Friday, April 9, 2021
3:30 PM
Physics Building, Room TBA
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Colloquium
Friday, April 16, 2021
3:30 PM
Online, Room via Zoom
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Colloquium
Friday, April 23, 2021
3:30 PM
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Colloquium
Friday, April 30, 2021
3:30 PM
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To add a speaker, send an email to bbc2x@Virginia.EDU Include the seminar type (e.g. Colloquia), date, name of the speaker, title of talk, and an abstract (if available). [Please send a copy of the email to phys-speakers@Virginia.EDU.]