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Search Results: 1 - 10 of 501795 matches for " Carlos A. Meriles "
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Rotating frame spin dynamics of a Nitrogen-Vacancy center in a diamond nanocrystal
Abdelghani Laraoui,Carlos A. Meriles
Physics , 2011, DOI: 10.1103/PhysRevB.84.161403
Abstract: We investigate the spin dynamics of a Nitrogen-Vacancy (NV) center contained in an individual diamond nanocrystal in the presence of continuous microwave excitation. Upon periodic reversal of the microwave phase, we observe a train of 'Solomon echoes' that effectively extends the system coherence lifetime to reach several tens of microseconds, depending on the microwave power and phase inversion rate. Starting from a model where the NV center interacts with a bath of paramagnetic defects on the nanocrystal surface, we use average Hamiltonian theory to compute the signal envelope from its amplitude at the echo maxima. Comparison between the effective Rabi and Solomon propagators shows that the observed response can be understood as a form of higher-order decoupling from the spin bath.
Imaging nuclear spins weakly coupled to a probe paramagnetic center
Abdelghani Laraoui,Daniela Pagliero,Carlos A. Meriles
Physics , 2015, DOI: 10.1103/PhysRevB.91.205410
Abstract: Optically-detected paramagnetic centers in wide-bandgap semiconductors are emerging as a promising platform for nanoscale metrology at room temperature. Of particular interest are applications where the center is used as a probe to interrogate other spins that cannot be observed directly. Using the nitrogen-vacancy center in diamond as a model system, we propose a new strategy to determining the spatial coordinates of weakly coupled nuclear spins. The central idea is to label the target nucleus with a spin polarization that depends on its spatial location, which is subsequently revealed by making this polarization flow back to the NV for readout. Using extensive analytical and numerical modeling, we show that the technique can attain high spatial resolution depending on the NV lifetime and target spin location. No external magnetic field gradient is required, which circumvents complications resulting from changes in the direction of the applied magnetic field, and considerably simplifies the required instrumentation. Extensions of the present technique may be adapted to pinpoint the locations of other paramagnetic centers in the NV vicinity or to yield information on dynamical processes in molecules on the diamond surface.
Generation of spin-polarized currents via cross-relaxation with dynamically pumped paramagnetic impurities
Carlos A. Meriles,Marcus W. Doherty
Physics , 2014, DOI: 10.1063/1.4890096
Abstract: Key to future spintronics and spin-based information processing technologies is the generation, manipulation, and detection of spin polarization in a solid state platform. Here, we theoretically explore an alternative route to spin injection via the use of dynamically polarized nitrogen-vacancy (NV) centers in diamond. We focus on the geometry where carriers and NV centers are confined to proximate, parallel layers and use a 'trap-and-release' model to calculate the spin cross-relaxation probabilities between the charge carriers and neighboring NV centers. We identify near-unity regimes of carrier polarization depending on the NV spin state, applied magnetic field, and carrier g-factor. In particular, we find that unlike holes, electron spins are distinctively robust against spin-lattice relaxation by other, unpolarized paramagnetic centers. Further, the polarization process is only weakly dependent on the carrier hopping dynamics, which makes this approach potentially applicable over a broad range of temperatures.
Recursive polarization of nuclear spins in diamond at arbitrary magnetic fields
Daniela Pagliero,Abdelghani Laraoui,Jacob D. Henshaw,Carlos A. Meriles
Physics , 2014, DOI: 10.1063/1.4903799
Abstract: We introduce an alternate route to dynamically polarize the nuclear spin host of nitrogen-vacancy (NV) centers in diamond. Our approach articulates optical, microwave and radio-frequency pulses to recursively transfer spin polarization from the NV electronic spin. Using two complementary variants of the same underlying principle, we demonstrate nitrogen nuclear spin initialization approaching 80% at room temperature both in ensemble and single NV centers. Unlike existing schemes, our approach does not rely on level anti-crossings and is thus applicable at arbitrary magnetic fields. This versatility should prove useful in applications ranging from nanoscale metrology to sensitivity-enhanced NMR.
Magnetometry of random AC magnetic fields using a single Nitrogen-Vacancy center
Abdelghani Laraoui,Jonathan S. Hodges,Carlos A. Meriles
Physics , 2010, DOI: 10.1063/1.3497004
Abstract: We report on the use of a single NV center to probe fluctuating AC magnetic fields. Using engineered currents to induce random changes in the field amplitude and phase, we show that stochastic fluctuations reduce the NV center sensitivity and, in general, make the NV response field-dependent. We also introduce two modalities to determine the field spectral composition, unknown a priori in a practical application. One strategy capitalizes on the generation of AC-field-induced coherence 'revivals', while the other approach uses the time-tagged fluorescence intensity record from successive NV observations to reconstruct the AC field spectral density. These studies are relevant for magnetic sensing in scenarios where the field of interest has a non-trivial, stochastic behavior, such as sensing unpolarized nuclear spin ensembles at low static magnetic fields.
The diamond Nitrogen-Vacancy center as a probe of random fluctuations in a nuclear spin ensemble
Abdelghani Laraoui,Jonathan S. Hodges,Colm Ryan,Carlos A. Meriles
Physics , 2011, DOI: 10.1103/PhysRevB.84.104301
Abstract: New schemes that exploit the unique properties of Nitrogen-Vacancy (NV) centers in diamond are presently being explored as a platform for high-resolution magnetic sensing. Here we focus on the ability of a NV center to monitor an adjacent mesoscopic nuclear spin bath. For this purpose, we conduct comparative experiments where the NV spin evolves under the influence of surrounding 13C nuclei or, alternatively, in the presence of asynchronous AC fields engineered to emulate bath fluctuations. Our study reveals substantial differences that underscore the limitations of the semi-classical picture when interpreting and predicting the outcome of experiments designed to probe small nuclear spin ensembles. In particular, our study elucidates the NV center response to bath fluctuations under common pulse sequences, and explores a detection protocol designed to probe time correlations of the nuclear spin bath dynamics. Further, we show that the presence of macroscopic nuclear spin order is key to the emergence of semi-classical spin magnetometry.
Near-band-gap photo-induced nuclear spin dynamics in semi-insulating GaAs: Hyperfine- and quadrupolar-driven relaxation
Yunpu Li,Jonathan P. King,Jeffrey A. Reimer,Carlos A. Meriles
Physics , 2014,
Abstract: Understanding and manipulating spin polarization and transport in the vicinity of semiconductor-hosted defects is a problem of present technological and fundamental importance. Here, we use high-field magnetic resonance to monitor the relaxation dynamics of spin-3/2 nuclei in semi-insulating GaAs. Our experiments benefit from the conditions created in the limit of low illumination intensities, where intermittent occupation of the defect site by photo-excited electrons leads to electric field gradient fluctuations and concomitant spin relaxation of the neighboring quadrupolar nuclei. We find indication of a heterogeneous distribution of polarization, governed by different classes of defects activated by either weak or strong laser excitation. Upon application of a train of light pulses of variable repetition rate and on/off ratio, we uncover an intriguing regime of mesoscale nuclear spin diffusion restricted by long-range, non-uniform electric field gradients. Given the slow time scale governing nuclear spin evolution, such optically-induced polarization patterns could be exploited as a contrast mechanism to expose dark lattice defects or localized charges with nanoscale resolution.
Correlation of maturity groups with seed composition in soybeans, as influenced by genotypic variation.
Maestri, Damián M.,Meriles, José M.,Guzmán, Carlos A.
Grasas y Aceites , 1998,
Abstract: Seeds of 19 soybean cultivars (Glycine max (L.) Merrill) with maturity groups V, VI or VII were analyzed for proximate composition, fatty acids and sterols. Protein, oil, carbohydrate and ash contents varied between 344-463 g kg-1, 178-233 g kg-1, 234-338 g kg-1, and 40.0-49.3 g kg-1 of dry matter, respectively. Fatty acid profiles revealed that the major acids were palmitic (9.2-12.5%), oleic (17.7-22.1%) and linoleic (53.6-56.9%). Linolenic acid ranged from 8.6 to 10.4%. Sitosterol (48.1-56.8%) was the main component of the sterol fraction, followed by campesterol (18.4-21.7%) and stigmasterol (13.4-18.0%). Statistically significant differences between genotypes were found for the majority of parameters evaluated, but there are not significant variations among maturity groups. Se analizaron la humedad, contenido en proteínas, carbohidratos, grasas y cenizas, y las composiciones en ácidos grasos y esteróles de las semillas de 19 cultivares de soja (Glycine max (L.) Merrill) con grupos de madurez V, VI o VIl. Los contenidos de proteínas, aceites, carbohidratos y cenizas variaron entre 344-463 g kg-1, 178-233 g kg-1, 234-338 g kg-1 y 40.0-49.3 g kg-1 de materia seca, respectivamente. Los ácidos grasos mayoritarios fueron palmítico (9.2-12.5%), oleico (17.7-22.1%) y linoleico (53.6-56.9%). El porcentaje de ácido linolénico varió desde 8.6 hasta 10.4%. El principal componente de la fracción de esteroles del aceite fue el sitosterol (48.1-56.8%), seguido por el campesterol (18.4-21.7%) y el estigmasterol (13.4-18.0%). Se encontraron diferencias estadísticamente significativas entre los genotipos para la mayoría de los parámetros evaluados, pero no hubo variaciones significativas entre grupos de madurez.
High-Resolution Correlation Spectroscopy of 13C Spins Near a Nitrogen-Vacancy Center in Diamond
Abdelghani Laraoui,Florian Dolde,Christian Burk,Friedemann Reinhard,J?rg Wrachtrup,Carlos A. Meriles
Physics , 2013, DOI: 10.1038/ncomms2685
Abstract: Spin complexes comprising the nitrogen-vacancy (NV) center and neighboring spins are being considered as a building block for a new generation of spintronic and quantum information processing devices. Because assembling identical spin clusters is difficult, new strategies are in order to determine individual node structures with the highest precision. Here we use a pulse protocol to monitor the time evolution of the 13C ensemble in the vicinity of a NV center. We observe long-lived time correlations in the nuclear spin dynamics, limited by NV spin-lattice relaxation. We use the host 14N spin as a quantum register, and demonstrate that hyperfine-shifted resonances can be separated upon proper NV initialization. Intriguingly, we find that the amplitude of the correlation signal exhibits a sharp dependence on the applied magnetic field. We discuss this observation in the context of the quantum-to-classical transition proposed recently to explain the field dependence of the spin cluster dynamics.
Imaging thermal conductivity with nanoscale resolution using a scanning spin probe
Abdelghani Laraoui,Halley Aycock-Rizzo,Yang Gao,Xi Lu,Elisa Riedo,Carlos A. Meriles
Physics , 2015, DOI: 10.1038/ncomms9954
Abstract: The ability to probe nanoscale heat flow in a material is often limited by lack of spatial resolution. Here, we use a diamond-nanocrystal-hosted nitrogen-vacancy centre attached to the apex of a silicon thermal tip as a local temperature sensor. We apply an electrical current to heat up the tip and rely on the NV to monitor the thermal changes the tip experiences as it is brought into contact with surfaces of varying thermal conductivity. With the aid of a combined AFM/confocal setup, we image phantom microstructures with nanoscale resolution, and attain excellent agreement between the thermal conductivity and topographic maps. The small mass and high thermal conductivity of the diamond host make the time response of our technique short, which we demonstrate by monitoring the tip temperature upon application of a heat pulse. Our approach promises multiple applications, from the investigation of phonon dynamics in nanostructures to the characterization of heterogeneous phase transitions and chemical reactions in various solid-state systems.
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