A5001822917- Semiconductor Quantum Structures and Devices
- Diamond and Carbon-based Materials Research
- Quantum Dots Synthesis And Properties
- Quantum and electron transport phenomena
- Chalcogenide Semiconductor Thin Films
- Advanced Semiconductor Detectors and Materials
- High-pressure geophysics and materials
- Force Microscopy Techniques and Applications
- Electronic and Structural Properties of Oxides
- Semiconductor materials and devices
- Atomic and Subatomic Physics Research
- Advanced Fiber Laser Technologies
- Advanced Surface Polishing Techniques
- Laser Design and Applications
- Ion-surface interactions and analysis
- Spectroscopy and Laser Applications
- Semiconductor Lasers and Optical Devices
- Molecular Junctions and Nanostructures
- Terahertz technology and applications
- 2D Materials and Applications
- Plasmonic and Surface Plasmon Research
- Advanced Fluorescence Microscopy Techniques
- Nonlinear Optical Materials Research
- Advanced X-ray Imaging Techniques
- Advanced Electron Microscopy Techniques and Applications
Indian Institute of Technology Madras
2024
London Centre for Nanotechnology
2020-2024
University College London
2020-2024
City College of New York
2016-2019
City University of New York
2013-2019
Queens College, CUNY
2012-2018
The Graduate Center, CUNY
2012-2018
The negatively charged nitrogen vacancy (NV-) center in diamond is the focus of widespread attention for applications ranging from quantum information processing to nanoscale metrology. Although most work so far has focused on NV- optical and spin properties, control charge state promises complementary opportunities. One intriguing possibility long-term storage information, a notion we hereby introduce using NV-rich, type 1b diamond. As proof principle, use multicolor microscopy read, write,...
Dynamic nuclear polarization via contact with electronic spins has emerged as an attractive route to enhance the sensitivity of magnetic resonance (NMR) beyond traditional limits imposed by field strength and temperature. Among various alternative implementations, use nitrogen vacancy (NV) centers in diamond - a paramagnetic point defect whose spin can be optically polarized at room temperature attracted widespread attention, but applications have been hampered need align NV axis external...
Although the spin properties of superficial shallow nitrogen-vacancy (NV) centers have been subject extensive scrutiny, considerably less attention has devoted to studying dynamics NV charge conversion near diamond surface. Using multicolor confocal microscopy, here we show that near-surface point defects arising from high-density ion implantation dramatically increase ionization and recombination rates NVs compared those in bulk diamond. Further, find these grow linearly, not quadratically,...
Abstract The nitrogen-vacancy (NV) centre in diamond is emerging as a promising platform for solid-state quantum information processing and nanoscale metrology. Of interest these applications the manipulation of NV charge, which can be attained by optical excitation. Here, we use two-colour microscopy to investigate dynamics photo-ionization, charge diffusion trapping type-1b diamond. We combine fixed-point laser excitation scanning fluorescence imaging locally alter concentration negatively...
Point defects in wide-band-gap semiconductors are emerging as versatile resources for nanoscale sensing and quantum information science, but our understanding of the photoionization dynamics is presently incomplete. Here, we use two-color confocal microscopy to investigate charge type 1b diamond hosting nitrogen-vacancy (NV) silicon-vacancy (SiV) centers. By examining nonlocal fluorescence patterns from local laser excitation, show that, simultaneous presence photogenerated electrons holes,...
One of the most remarkable properties nitrogen-vacancy (NV) center in diamond is that optical illumination initializes its electronic spin almost completely, a feature can be exploited to polarize other species their proximity. Here we use field-cycled nuclear magnetic resonance (NMR) investigate mechanisms polarization transfer from NVs 13C spins at room temperature. We focus on dynamics near 51 mT, where fortuitous combination energy matching conditions between electron and levels gives...
There has been tremendous progress in the physical realization of quantum computing hardware recent times, bringing us closer than ever before to realizing promise computing. However, noise continues pose a crucial challenge when it comes scaling up present day processors. While decoherence limits qubits ability store information for long periods presence uncontrollable sources, erroneous implementation control methods state preparation and measurements leads faulty implementations circuits....
A broad effort is underway to improve the sensitivity of nuclear magnetic resonance through use dynamic polarization. Nitrogen-vacancy (NV) centers in diamond offer an appealing platform because these paramagnetic defects can be optically polarized efficiently at room temperature. However, work thus far has been mainly limited single crystals most polarization transfer protocols are sensitive misalignment between NV and field axes. Here we study spin dynamics NV-13C pairs simultaneous...
We study the photophysical stability of ensemble near-surface nitrogen vacancy (NV) centers in diamond under vacuum and air. The optically detected magnetic resonance contrast NV was measured following exposure to laser illumination, showing opposing trends air compared (increasing by up 9% dropping 25%, respectively). Characterization using X-ray photoelectron spectroscopy (XPS) suggests a surface reconstruction: In air, atmospheric oxygen adsorption on leads an increase NV– fraction,...
We demonstrate optical readout of ensembles nitrogen-vacancy(NV) center spins in a bulk diamond sample via spin-to-charge conversion. A high power 594 nm laser is utilized to selectively ionize these paramagnetic defects the spin state with contrast up 12%. In comparison conventional 520 readout, spin-to-charge-conversion-based provides higher signal-to-noise ratio, tenfold sensing measurement speedup for millisecond long pulse sequences. This level performance was achieved an NV- ionization...
A neural network is constructed to learn the environment of an arbitrary qubit, allowing underlying noise spectrum be extracted in a manner that more accurate and experimentally efficient than existing methods.
A spectral analysis of the Aharonov-Bohm (AB) oscillation in magneto-photoluminescence intensity was performed for stacked type-II ZnTe/ZnSe quantum dots (QDs). Very narrow AB oscillations (∼0.3 T) allowed probing both lateral size distribution stack ensemble QDs and excitons as determined by electronic orbit with sub-nanometer precision. Two sets stacks excitonic 18.2 17.5 nm are to be present sample.
Abstract In this article, we explore the effect of two different infrared (IR) laser wavelengths on optical properties trapped nano-diamonds containing high-density ensembles nitrogen vacancy (NV) centers. We investigate 975 nm and 1064nm for trapping lasers find that NV photoluminescence quenching is more prominent illumination than when simultaneously excited with a 532 laser. order to understand underlying mechanism, develop rate-equation-based model takes into account various transition...
High resolution x-ray diffraction based reciprocal space mapping is employed to investigate vertical correlation in submonolayer Zn(Cd)Te/ZnCdSe type-II quantum dots (QDs). The average lateral deviation from one dot another found decrease 13%–17% 8%–11% with an increase QD size. Narrower photoluminescence a better yield obtained for the sample improved correlation, indicating smaller size distribution along partial suppression of non-radiative recombination paths. Observed reduction...
Sub-monolayer quantities of Mg are introduced in multilayer stacked ZnMgTe quantum dots (QDs) embedded ZnSe barriers order to reduce the hole confinement energy by controlling bandgaps and band-offsets ZnTe/ZnSe system having type-II band alignment. The photoluminescence (PL) emission from such ZnMgTe/ZnSe QD structure is found be a broad centered at 2.35 eV. higher side PL shows larger blue-shift with increasing excitation intensity faster life-time decay due greater contribution smaller...
Quantum cascade (QC) lasers with emission at wavelengths below 4 μm are difficult to achieve from conventional III-V materials systems lattice matched GaAs and InP due the limited conduction band offset (CBO) of those that results presence intervalley scattering. The II-VI ZnCdSe/ZnCdMgSe, a CBO as high 1.12 eV no scattering, promising candidates this goal. Using molecular beam epitaxy (MBE), authors grew QC laser structure three-well active region design made ZnCdSe ZnCdMgSe multilayers...
For submonolayer quantum dot (QD) based photonic devices, size and density of QDs are critical parameters, the probing which requires indirect methods. We report determination lateral distribution type-II ZnTe/ZnSe stacked QDs, on spectral analysis optical signature Aharanov-Bohm (AB) excitons, complemented by photoluminescence studies, secondary-ion mass spectroscopy, numerical calculations. Numerical calculations employed to determine AB transition magnetic field as a function QD radius....
Intermediate band solar cells (IBSCs) have been predicted to be significantly more efficient than the conventional cells, but not realized their full potential due difficulties related fabrication of practical devices. The authors report here on growth and characterization Zn(Cd)Te/ZnCdSe submonolayer quantum dot (QD) superlattices (SLs), grown by migration enhanced epitaxy. These QDs do exhibit formation wetting layers, which is one culprits for unsatisfactory performance IBSCs. ZnCdSe host...
Robust and narrow Aharonov-Bohm (AB) oscillations were observed in magneto-photoluminescence intensity of stacked ZnTe/ZnSe quantum dots (QDs) due to the presence built-in electric field. A spectral analysis such AB allowed for qualitative probing lateral size type-II excitons. Two samples grown using different growth sequences analyzed compared. The magnetic field value at which transition takes place changed across spectra one samples, indicating a two distinct QD stacks; ``double peak''...
We describe a procedure for the morphological characterization of hard-to-image submonolayer quantum dot structures. This employs high resolution x-ray diffraction based reciprocal space mapping, accompanied by rigorous modeling precise determination morphology dots. Our modelling results and experimental data clearly show that investigated dots are anisotropically elongated along [110] orientation. Complementary polarization dependent photoluminescence measurements, combined with our...
We examine the temperature dependence of visibility excitonic Aharonov-Bohm peak in type-II quantum dots. obtain a functional that is similar to determined by transport experiments, namely, with ${T}^{\ensuremath{-}1}$ term due electron-electron collisions and ${T}^{\ensuremath{-}3}$ electron-phonon interactions. However, magnitude latter much smaller than for electrons interaction strength exciton-phonon coupling. Such suppressed ushers way all-optical studies decoherence processes...