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Dive into the research topics where M. Javani is active.

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Featured researches published by M. Javani.


Physical Review Letters | 2016

Real and Imaginary Properties of Epsilon-Near-Zero Materials

M. Javani; Mark I. Stockman

From the fundamental principle of causality we show that epsilon-near-zero (ENZ) materials with a very low (asymptotically zero) intrinsic dielectric loss do necessarily possess a very low (asymptotically zero) group velocity of electromagnetic wave propagation. This leads to the loss function being singular and causes high nonradiative damping of the optical resonators and emitters (plasmonic nanoparticles, quantum dots, chromophore molecules) embedded into them or placed at their surfaces. Rough ENZ surfaces do not exhibit hot spots of local fields suggesting that surface modes are overdamped. Reflectors and waveguides also show very large losses both for realistic and idealized ENZ materials.


Light-Science & Applications | 2016

Nanoscopy reveals surface-metallic black phosphorus

Yohannes Abate; Sampath Gamage; Zhen Li; Viktoriia E. Babicheva; M. Javani; Han Wang; Stephen B. Cronin; Mark I. Stockman

Black phosphorus (BP) is an emerging two-dimensional material with intriguing physical properties. It is highly anisotropic and highly tunable by means of both the number of monolayers and surface doping. Here, we experimentally investigate and theoretically interpret the near-field properties of a-few-atomic-monolayer nanoflakes of BP. We discover near-field patterns of bright outside fringes and a high surface polarizability of nanofilm BP consistent with its surface-metallic, plasmonic behavior at mid-infrared frequencies <1176 cm−1. We conclude that these fringes are caused by the formation of a highly polarizable layer at the BP surface. This layer has a thickness of ~1 nm and exhibits plasmonic behavior. We estimate that it contains free carriers in a concentration of n≈1.1 × 1020 cm−3. Surface plasmonic behavior is observed for 10–40 nm BP thicknesses but absent for a 4-nm BP thickness. This discovery opens up a new field of research and potential applications in nanoelectronics, plasmonics and optoelectronics.


Scientific Reports | 2015

Control of Plasmonic Nanoantennas by Reversible Metal-insulator Transition

Yohannes Abate; Robert E. Marvel; Jed I. Ziegler; Sampath Gamage; M. Javani; Mark I. Stockman; Richard F. Haglund

We demonstrate dynamic reversible switching of VO2 insulator-to-metal transition (IMT) locally on the scale of 15 nm or less and control of nanoantennas, observed for the first time in the near-field. Using polarization-selective near-field imaging techniques, we simultaneously monitor the IMT in VO2 and the change of plasmons on gold infrared nanoantennas. Structured nanodomains of the metallic VO2 locally and reversibly transform infrared plasmonic dipole nanoantennas to monopole nanoantennas. Fundamentally, the IMT in VO2 can be triggered on femtosecond timescale to allow ultrafast nanoscale control of optical phenomena. These unique features open up promising novel applications in active nanophotonics.


European Physical Journal D | 2016

Coherence of Auger and inter-Coulombic decay processes in the photoionization of Ar@C60 versus Kr@C60

Maia Magrakvelidze; Ruma De; M. Javani; Mohamed Madjet; Steven T. Manson; Himadri Chakraborty

Abstract For the asymmetric spherical dimer of an endohedrally confined atom and a host fullerene, an innershell vacancy of either system can decay through the continuum of an outer electron hybridized between the systems. Such decays, viewed as coherent superpositions of the single-center Auger and two-center inter-Coulombic (ICD) amplitudes, are found to govern leading decay mechanisms in noble-gas endofullerenes, and are likely omnipresent in this class of nanomolecules. A comparison between resulting autoionizing resonances calculated in the photoionization of Ar@C60 and Kr@C60 exhibits details of the underlying processes. Graphical abstract


Physical Review A | 2014

Resonant Auger-intersite-Coulombic hybridized decay in the photoionization of endohedral fullerenes

M. Javani; Jacob Wise; Ruma De; Mohamed Madjet; Steven T. Manson; Himadri Chakraborty

Considering the photoionization of Ar@C60, we predict resonant femtosecond decays of both Ar and C60 vacanciesthroughthecontinuaofatom-fullerenehybridfinalstates.ForAr3s → np excitations,theseresonances are far stronger than the Ar-to-C60 resonant intersite-Coulombic decays (ICD), while for C60 excitations they are strikingly larger than the corresponding Auger features. The results indicate the power of hybridization to enhance decay rates and modify lifetimes and line profiles, offering a unique probe, more powerful than regular ICDs, for multicenter decay processes.


Journal of Physics B | 2014

Photoionization of bonding and antibonding-type atom-fullerene hybrid states in Cd@C60 vs Zn@C60

M. Javani; Ruma De; Mohamed Madjet; Steven T. Manson; Himadri Chakraborty

Powerful hybridization of the Cd 4d state with the d-angular momentum state of C60 π symmetry is found in the local density approximation (LDA) structure of Cd@C60 ground state. The photoionization of the resulting symmetric and antisymmetric levels are computed using the time dependent LDA method to include electron correlations. Cross sections exhibit effects of the C60 plasmonic motion coherently coupled to the diffraction-type cavity oscillations induced by local emissions from C60. The Cd@C60 results exhibit a substantial difference from our previous results for Zn@C60.


European Physical Journal D | 2012

Valence photoionization of small alkaline earth atoms endohedrally confined in C60

M. Javani; M. R. McCreary; Aakash Patel; Mohamed Madjet; Himadri Chakraborty; S. T. Manson


arXiv: Mesoscale and Nanoscale Physics | 2015

Nanoscopy Reveals Metallic Black Phosphorus

Yohannes Abate; Sampath Gamage; Li Zhen; Stephen B. Cronin; Han Wang; Viktoriia E. Babicheva; M. Javani; Mark I. Stockman


Physical Review A | 2012

Atom-fullerene-hybrid photoionization mediated by coupled d states in Zn@C 60

Jaykob N. Maser; M. Javani; Ruma De; Mohamed Madjet; Himadri Chakraborty; Steven T. Manson


Bulletin of the American Physical Society | 2016

Inter-Coulombic decay (ICD) of endofullerene inner-vacancies in coherence with the Auger decay

Maia Magrakvelidze; Ruma De; M. Javani; Mohamed Madjet; Steven T. Manson; Himadri Chakraborty

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Himadri Chakraborty

Northwest Missouri State University

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Ruma De

Northwest Missouri State University

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S. T. Manson

Georgia State University

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Sampath Gamage

Georgia State University

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Yohannes Abate

Georgia State University

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Aakash Patel

Northwest Missouri State University

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Han Wang

University of Southern California

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