Nathaniel Brady
University of Alabama at Birmingham
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Publication
Featured researches published by Nathaniel Brady.
Nano Letters | 2014
Kannatassen Appavoo; Bin Wang; Nathaniel Brady; Minah Seo; Joyeeta Nag; Rohit P. Prasankumar; David J. Hilton; Sokrates T. Pantelides; Richard F. Haglund
Ultrafast photoinduced phase transitions could revolutionize data-storage and telecommunications technologies by modulating signals in integrated nanocircuits at terahertz speeds. In quantum phase-changing materials (PCMs), microscopic charge, lattice, and orbital degrees of freedom interact cooperatively to modify macroscopic electrical and optical properties. Although these interactions are well documented for bulk single crystals and thin films, little is known about the ultrafast dynamics of nanostructured PCMs when interfaced to another class of materials as in this case to active plasmonic elements. Here, we demonstrate how a mesh of gold nanoparticles, acting as a plasmonic photocathode, induces an ultrafast phase transition in nanostructured vanadium dioxide (VO2) when illuminated by a spectrally resonant femtosecond laser pulse. Hot electrons created by optical excitation of the surface-plasmon resonance in the gold nanomesh are injected ballistically across the Au/VO2 interface to induce a subpicosecond phase transformation in VO2. Density functional calculations show that a critical density of injected electrons leads to a catastrophic collapse of the 6 THz phonon mode, which has been linked in different experiments to VO2 phase transition. The demonstration of subpicosecond phase transformations that are triggered by optically induced electron injection opens the possibility of designing hybrid nanostructures with unique nonequilibrium properties as a critical step for all-optical nanophotonic devices with optimizable switching thresholds.
Journal of Physics: Condensed Matter | 2016
Nathaniel Brady; Kannatassen Appavoo; Minah Seo; Joyeeta Nag; Rohit P. Prasankumar; Richard F. Haglund; David J. Hilton
We report on ultrafast optical investigations of the light-induced insulator-to-metal phase transition in vanadium dioxide with controlled disorder generated by substrate mismatch. These results reveal common dynamics of this optically-induced phase transition that are independent of this disorder. Above the fluence threshold for completing the transition to the rutile crystalline phase, we find a common time scale, independent of sample morphology, of 40.5 ± 2 ps that is consistent with nucleation and growth dynamics of the R phase from the parent M1 ground state.
European Physical Journal B | 2013
Nathaniel Brady; Jeffrey Montgomery; Georgiy M. Tsoi; T. Gebre; Samuel T. Weir; Yogesh K. Vohra; D. J. Hilton
Bulletin of the American Physical Society | 2015
Nathaniel Brady; Kannatassen Appavoo; Joyeeta Nag; Minah Seo; Rohit P. Prasankumar; Richard F. Haglund; David J. Hilton
Bulletin of the American Physical Society | 2014
Nathaniel Brady; Kannatassen Appavoo; Rohit P. Prasankumar; Richard F. Haglund; David J. Hilton
EPJ Web of Conferences | 2013
Kannatassen Appavoo; Nathaniel Brady; Minah Seo; Joyeeta Nag; Rohit P. Prasankumar; David J. Hilton; Richard F. Haglund
EPJ Web of Conferences | 2013
Nathaniel Brady; Kannatassen Appavoo; Minah Seo; Joyeeta Nag; Rohit P. Prasankumar; Richard F. Haglund; David J. Hilton
Bulletin of the American Physical Society | 2013
Bin Wang; Kannatassen Appavoo; Nathaniel Brady; Minah Seo; Joyeeta Nag; Rohit P. Prasankumar; David J. Hilton; Richard F. Haglund; Sokrates T. Pantelides
Bulletin of the American Physical Society | 2013
Nathaniel Brady; Kannatassen Appavoo; Jeffery Montgomery; Yogesh K. Vohra; Richard F. Haglund; David J. Hilton
conference on lasers and electro optics | 2012
Kannatassen Appavoo; Nathaniel Brady; Minah Seo; Joyeeta Nag; Rohit P. Prasankumar; David J. Hilton; Richard F. Haglund