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AEP Faculty Candidate Seminar - Dr. Georgios Varnavides

Monday, February 19, 2024 at 11:00am to 12:00pm

Clark Hall, 700
Central Campus

Exotic Current Densities and How to (Computationally) Image Them

Dr. Georgios Varnavides
Postdoctoral Research Fellow
University of California, Berkeley

With data centers projected to make up as high as 8% of global demand by 2030, there is a pressing need to design energy-efficient electronic devices using bottom-up techniques. However, two of the most promising platforms for the continued downsizing of transistors in integrated circuits face fundamental physical limitations such as heat dissipation. More broadly, the miniaturization of electronic devices implies the transport of charge, heat, and spin in these devices results in spatially-varying signatures with strong implications in materials properties. For example, recent advances in transport measurements have revealed that electrons in materials can flow collectively, exhibiting fluid phenomena such as channel flow and vortices. Observations of these charged electron fluids re-invigorated the half-century-old field of "electron hydrodynamics" and hold promise in designing energy-efficient electronic devices. In the first part of the talk, I will introduce electron fluids, highlighting their novel anisotropic and non-dissipative viscous contributions enabled by preferred directions in crystalline solids, and discuss the observation of electron fluids in a high-carrier-density conductor for the first time.

The complex spatial-signatures these viscous fluids admit exceed current resolution capabilities, necessitating the development of new imaging modalities to image current densities (and fields more generally) with high spatial resolution. In the second part of the talk, I will propose the use of computational imaging techniques -- i.e. the use of algorithms to reconstruct an image from non-directly interpretable detector data -- as a tantalizing alternative to address this challenge. Specifically, I will formulate a novel phase-retrieval algorithm as an inverse scattering problem and demonstrate its dose-efficiency with two complimentary applications: imaging the weak magnetization of anti-ferromagnets with atomic resolution, and achieving medium-resolution of frozen hydrated proteins using only several hundred reconstructed micrographs. Finally, I will discuss the possibility and challenges to extend these techniques to 3D in-situ and for larger biological volumes within cellular context.
About the speaker:
Georgios Varnavides is a postdoctoral Miller research fellow at the University of California, Berkeley, where he is developing new computational imaging modalities to observe structure and function in materials with high spatial resolution. Varnavides obtained his Ph.D. from the Massachusetts Institute of Technology with an award-winning thesis, titled "Electron Hydrodynamics in Crystalline Solids." Varnavides is originally from Cyprus where he grew up and studied before moving to the U.S. to obtain his BS in materials science & engineering and BS in civil and environmental engineering from MIT in 2017. Varnavides is the recipient of various fellowships and awards, including the Materials Research Society graduate student gold award and the John Wulff award for excellence in teaching an undergraduate subject.

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Applied and Engineering Physics

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engineering, applied and engineering physics

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Cheri Sigmund

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Dr. Georgio Varnavides

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Postdoctoral Research Fellow, University of California, Berkeley

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