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Featured researches published by Nathaniel Brady.


Nano Letters | 2014

Ultrafast Phase Transition via Catastrophic Phonon Collapse Driven by Plasmonic Hot-Electron Injection

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

Heterogeneous nucleation and growth dynamics in the light-induced phase transition in vanadium dioxide.

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

Equation of state and electrical resistivity of the heavy fermion superconductor CeCoIn 5 to 51 GPa

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

Heterogeneous Nucleation and Growth Dynamics in the Light-induced Phase Transition in Vanadium Dioxide

Nathaniel Brady; Kannatassen Appavoo; Joyeeta Nag; Minah Seo; Rohit P. Prasankumar; Richard F. Haglund; David J. Hilton


Bulletin of the American Physical Society | 2014

Disorder-dominated Ultrafast Dynamics in Vanadium Dioxide

Nathaniel Brady; Kannatassen Appavoo; Rohit P. Prasankumar; Richard F. Haglund; David J. Hilton


EPJ Web of Conferences | 2013

Ultrafast Phase Transition in Vanadium Dioxide Driven by Hot-Electron Injection

Kannatassen Appavoo; Nathaniel Brady; Minah Seo; Joyeeta Nag; Rohit P. Prasankumar; David J. Hilton; Richard F. Haglund


EPJ Web of Conferences | 2013

Ultrafast Dynamics of the VO2 Insulator-to-Metal Transition Observed by Nondegenerate Pump-Probe Spectroscopy

Nathaniel Brady; Kannatassen Appavoo; Minah Seo; Joyeeta Nag; Rohit P. Prasankumar; Richard F. Haglund; David J. Hilton


Bulletin of the American Physical Society | 2013

Plasmonic electron injection drives ultrafast phase transition by catastrophic phonon collapse I: experiment

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

High Pressure Crystalline Structure and Resistance of Vanadium Dioxide to 13.5 GPa

Nathaniel Brady; Kannatassen Appavoo; Jeffery Montgomery; Yogesh K. Vohra; Richard F. Haglund; David J. Hilton


conference on lasers and electro optics | 2012

Ultrafast metal-insulator transition in VO 2 driven by electron injection

Kannatassen Appavoo; Nathaniel Brady; Minah Seo; Joyeeta Nag; Rohit P. Prasankumar; David J. Hilton; Richard F. Haglund

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David J. Hilton

University of Alabama at Birmingham

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Rohit P. Prasankumar

Los Alamos National Laboratory

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Minah Seo

Korea Institute of Science and Technology

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Yogesh K. Vohra

University of Alabama at Birmingham

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Georgiy M. Tsoi

University of Alabama at Birmingham

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Bin Wang

University of Oklahoma

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