Gartstein, Yuri N.
Permanent URI for this collectionhttps://hdl.handle.net/10735.1/3901
Yuri Gartsein is an Associate Professor of Physics and an Affiliated Faculty member of the Alan G. MacDiarmid NanoTech Institute. "His research interests concentrate around theory and modeling of various physical properties of nanostructured systems, particularly in the context of light-matter interaction and processes of charge and energy transfer." Read more about Dr. Gartstein at his Physics Faculty Highlight, NanoTech Institute and Research Explorer pages.
Browse
Browsing Gartstein, Yuri N. by Issue Date
Now showing 1 - 7 of 7
- Results Per Page
- Sort Options
Item Energy Transfer from Colloidal Nanocrystals into Si Substrates Studied via Photoluminescence Photon Counts and Decay Kinetics(2013-08-16) Nguyen, H. M.; Seitz, Oliver; Gartstein, Yuri N.; Chabal, Yves J.; Malko, Anton V.; 0000 0001 2678 9765 (Malko, AV); Nguyen, H. M.; Seitz, Oliver; Gartstein, Yuri N.; Chabal, Yves J.; Malko, Anton V.We use time-resolved photoluminescence (PL) kinetics and PL intensity measurements to study the decay of photoexcitations in colloidal CdSe/ZnS nanocrystals grafted on SiO₂ - Si substrates with a wide range of the SiO₂ spacer layer thicknesses. The salient features of experimental observations are found to be in good agreement with theoretical expectations within the framework of modification of spontaneous decay of electric-dipole excitons by their environment. Analysis of the experimental data reveals that energy transfer (ET) from nanocrystals into Si is a major enabler of substantial variations in decay rates, where we quantitatively distinguish contributions from nonradiative and radiative ET channels. We demonstrate that time-resolved PL kinetics provides a more direct assessment of ET, while PL intensity measurements are also affected by the specifics of the generation and emission processes.Item Local Field Effects for Spherical Quantum Dot Emitters in the Proximity of a Planar Dielectric Interface(Optical Soc Amer, 2014-08-05) Gordon, Joseph M.; Gartstein, Yuri N.We use numerical solutions of macroscopic Maxwell's equations to study spontaneous emission rates of model spherical quantum dot (QD) emitters in the vicinity of a highly polarizable dielectric substrate. It is demonstrated that extra polarization of the QD body taking place in the interfacial region may lead to appreciable deviations from the rates that would be expected under the assumption of a fixed magnitude of the effective QD transition dipole moment. Illustrations are given for both radiative and nonradiative decay processes, and potential experimental implications are discussed.Item Exciton Polaritons in Transition-Metal Dichalcogenides and Their Direct Excitation via Energy Transfer(2015-08-28) Gartstein, Yuri N.; Li, Xiao; Zhang, Chuanwei; 6603852436 (Gartstein, Yuri)Excitons, composite electron-hole quasiparticles, are known to play an important role in optoelectronic phenomena in many semiconducting materials. Recent experiments and theory indicate that the band-gap optics of the newly discovered monolayer transition-metal dichalcogenides (TMDs) is dominated by tightly bound valley excitons. The strong interaction of excitons with long-range electromagnetic fields in these two-dimensional systems can significantly affect their intrinsic properties. Here, we develop a semiclassical framework for intrinsic exciton polaritons in monolayer TMDs that treats their dispersion and radiative decay on the same footing and can incorporate effects of the dielectric environment. It is demonstrated how both inter- and intravalley long-range interactions influence the dispersion and decay of the polaritonic eigenstates. We also show that exciton polaritons can be efficiently excited via resonance energy transfer from quantum emitters such as quantum dots, which may be useful for various applications.Item Charge Carrier Coherence and Hall Effect in Organic Semiconductors(Nature Publishing Group, 2016-03-30) Yi, H. T.; Gartstein, Yuri N.; Podzorov, V.; Gartstein, Yuri N.Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force acting on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor.Item Propagation and Absorption of Light in Planar Dielectric Waveguides with Two-Dimensional Semiconductors(Optical Soc Amer, 2017-09-12) Gartstein, Yuri N.; Malko, Anton V.; 0000 0001 2678 9765 (Malko, AV); Gartstein, Yuri N.; Malko, Anton V.Strong optical responses of atomically thin two-dimensional (2D) semiconductors make them attractive candidates for integration into various photonic and optoelectronic structures. We discuss some fundamental effects of such integration into planar dielectric waveguides by demonstrating that a substantial modification of the spectrum of waveguide modes can occur due to high in-plane polarizability of 2D layers. Our calculations illustrate both the conceptual possibilities associated with sharp excitonic resonances as well as the results obtained with the experimentally assessed polarizability of monolayer MoS2 over a broad spectral range. We point out that waveguide structures could also enable the tunable absorption by 2D semiconductors of the light that propagates along them, a modality quite different from the traditional light harvesting geometry.Item Energy Transfer from Colloidal Nanocrystals to Strongly Absorbing Perovskites(Royal Society of Chemistry, 2018-06-01) Cabrera, Yasiel; Rupich, Sara M.; Shaw, Ryan; Anand, Benoy; Villa, Manuel de Anda; Rahman, Rezwanur; Dangerfield, Aaron; Gartstein, Yuri N.; Malko, Anton V.; Chabal, Yves J.; 0000-0002-6435-0347 (Chabal, YJ); Cabrera, Yasiel; Rupich, Sara M.; Shaw, Ryan; Anand, Benoy; Villa, Manuel de Anda; Rahman, Rezwanur; Dangerfield, Aaron; Gartstein, Yuri N.; Malko, Anton V.; Chabal, Yves J.Integration of colloidal nanocrystal quantum dots (NQDs) with strongly absorbing semiconductors offers the possibility of developing optoelectronic and photonic devices with new functionalities. We examine the process of energy transfer (ET) from photoactive CdSe/ZnS core/shell NQDs into lead-halide perovskite polycrystalline films as a function of distance from the perovskite surface using time-resolved photoluminescence (TRPL) spectroscopy. We demonstrate near-field electromagnetic coupling between vastly dissimilar excitation in two materials that can reach an efficiency of 99% at room temperature. Our experimental results, combined with electrodynamics modeling, reveal the leading role of non-radiative ET at close distances, augmented by the waveguide emission coupling and light reabsorption at separations >10 nm. These results open the way to combining materials with different dimensionalities to achieve novel nanoscale architectures with improved photovoltaic and light emitting functionalities.Item HIF-1α-PDK1 Axis-Induced Active Glycolysis Plays an Essential Role in Macrophage Migratory Capacity(American Physical Society) Anand, Benoy; Sampat, Siddharth; Danilov, E. O.; Peng, Weina; Rupich, Sara M.; Chabal, Yves J.; Gartstein, Yuri N.; Malko, Anton V.; 0000 0001 1969 6683 (Gartstein, YN); 0000 0001 2678 9765 (Malko, AV); 170647442 (Gartstein, YN); Anand, Benoy; Sampat, Siddharth; Peng, Weina; Rupich, Sara M.; Chabal, Yves J.; Gartstein, Yuri N.; Malko, Anton V.Ultrafast transient pump-probe measurements of thin CH₃NH₃PbI₃ perovskite films over a wide spectral range from 350 to 800 nm reveal a family of photoinduced bleach (PB) and absorption (PA) features unequivocally pointing to the fundamentally multiband character of the underlying electronic structure. Excitation pump-energy dependent kinetics of three long-lived PB peaks at 1.65, 2.55, and 3.15 eV along with a broad PA band shows the involvement of band-edge thermalized carriers in all transitions and at least four, possibly more, electronic bands. The evolution of the transient signatures is described in terms of the redistribution of the conserved oscillator strength of the whole system. The multiband perspective opens up different directions for understanding and controlling photoexcitations in hybrid perovskites.