Dr. George Varnavides

Selected Awards and Fellowships

Dr. George Varnavides

Postdoctoral Scholar


George is originally from Cyprus where he grew up and studied before moving to the US to obtain his BS in materials science & engineering and BS in civil & environmental engineering from MIT in 2017. Enamored with the Boston weather, George decided to stay at MIT to pursue his graduate studies in the department of Materials Science, co-advised by Prof. Narang at Harvard, where he recently defended his thesis entitled “Electron Hydrodynamics in Crystalline Solids: Microscopic Origins, Mesoscopic Size Effects, and Macroscopic Observables”.

Currently, George is a postdoctoral Miller research fellow at the University of California, Berkeley – co-hosted by Prof. Mary Scott in MSE and Prof. Joel Moore in Physics – where he’s developing new computational imaging modalities to observe current densities in anisotropic electron fluids with high spatial resolution using a transmission electron microscope.

When he doesn’t have his science cap on, George enjoys camping, teaching generative art, and singing along to musical theater videos.

Publications

  • Read the full paper here! Abstract Polar dielectrics are key materials of interest for infrared (IR) nanophotonic applications due to their ability to host phonon-polaritons (PhPs) that allow for low-loss, subdiffractional control of light. The properties of phonon-polaritons are limited by the characteristics of optical phonons, which are nominally fixed for most “bulk” materials. Superlattices composed of alternating atomically-thin materials offer control over crystal anisotropy through changes in composition, optical phonon confinement, and the emergence of new modes. In particular, the modified optical phonons in superlattices offer the potential for so-called crystalline hybrids whose IR properties cannot be described as a simple mixture of the bulk constituents. To date, however, studies have primarily focused on identifying the presence of new or modified optical phonon modes rather than assessing their impact on the IR response. This study focuses on assessing the impact of confined optical phonon modes on the hybrid IR dielectric function in superlattices of GaSb and AlSb. Using a combination of first principles theory, Raman, FTIR, and spectroscopic ellipsometry, the hybrid dielectric function is found to track with the confinement of optical phonons, leading to optical phonon spectral shifts of up to 20 cm−1. These results provide an alternative pathway towards designer IR optical materials.