arXiv subjects

Siddharth Dhomkar

Publications and source records attributed to Siddharth Dhomkar.

23 records · Page 2Linked to original sources

arXiv2018

Charge dynamics in near-surface, variable-density ensembles of nitrogen-vacancy centers in diamond

Although the spin properties of superficial shallow nitrogen-vacancy (NV) centers have been the subject of extensive scrutiny, considerably less attention has been devoted to studying the dynamics of NV charge conversion near the diamond surface. Using multi-color confocal microscopy, here we show that near-surface point defects arising from high-density ion implantation dramatically increase the ionization and recombination rates of shallow NVs compared to those in bulk diamond. Further, we find that these rates grow linearly not quadratically with laser intensity, indicative of single-photon processes enabled by NV state mixing with other defect states. Accompanying these findings we observe NV ionization and recombination in the dark, likely the result of charge transfer to neighboring traps. In spite of the altered charge dynamics, we show one can imprint rewritable, long-lasting patterns of charged-initialized, near-surface NVs over large areas, an ability that could be exploited for electrochemical biosensing or to optically store digital data sets with sub-diffraction resolution.

cond-mat.mes-hall↗

arXiv2018

On-Demand Generation of Neutral and Negatively-Charged Silicon-Vacancy Centers in Diamond

Point defects in wide-bandgap semiconductors are emerging as versatile resources for nanoscale sensing and quantum information science but our understanding of the photo-ionization dynamics is presently incomplete. Here we use two-color confocal microscopy to investigate the dynamics of charge in Type 1b diamond hosting nitrogen-vacancy (NV) and silicon-vacancy (SiV) centers. By examining the non-local fluorescence patterns emerging from local laser excitation, we show that in the simultaneous presence of photo-generated electrons and holes, SiV (NV) centers selectively transform into the negative (neutral) charge state. Unlike NVs, 532 nm illumination ionizes SiV- via a single photon process thus hinting at a comparatively shallower ground state. In particular, slower ionization rates at longer wavelengths suggest the latter lies approximately ~1.9 eV below the conduction band minimum. Building on the above observations we demonstrate on-demand SiV and NV charge initialization over large areas via green laser illumination of variable intensity.

cond-mat.mes-hall↗

arXiv2017

Multi-spin-assisted optical pumping of bulk 13C nuclear spin polarization in diamond

One of the most remarkable properties of the nitrogen-vacancy (NV) center in diamond is that optical illumination initializes its electronic spin almost completely, a feature that can be exploited to polarize other spin species in their proximity. Here we use field-cycled nuclear magnetic resonance (NMR) to investigate the mechanisms of spin polarization transfer from NVs to 13C spins in diamond at room temperature. We focus on the dynamics near 51 mT, where a fortuitous combination of energy matching conditions between electron and nuclear spin levels gives rise to alternative polarization transfer channels. By monitoring the 13C spin polarization as a function of the applied magnetic field, we show 13C spin pumping takes place via a multi-spin cross relaxation process involving the NV- spin and the electronic and nuclear spins of neighboring P1 centers. Further, we find that this mechanism is insensitive to the crystal orientation relative to the magnetic field, although the absolute level of 13C polarization - reaching up to ~3% under optimal conditions - can vary substantially depending on the interplay between optical pumping efficiency, photo-generated carriers, and laser-induced heating.

quant-ph↗

arXiv2016

Long-term data storage in diamond

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 the NV- optical and spin properties, control of the charge state promises complementary opportunities. One intriguing possibility is the long-term storage of information, a notion we hereby introduce using NV rich, type-1b diamond. As a proof of principle, we use multi-color optical microscopy to read, write, and reset arbitrary data sets with 2-D binary bit density comparable to present digital-video-disk (DVD) technology. Leveraging on the singular dynamics of NV- ionization, we encode information on different planes of the diamond crystal with no cross talk, hence extending the storage capacity to three dimensions. Further, we correlate the center's charge state and nuclear spin polarization of the nitrogen host, and show that the latter is robust to a cycle of NV- ionization and recharge. In combination with super-resolution microscopy techniques, these observations provide a route towards sub-diffraction NV charge control, a regime where the storage capacity could exceed present technologies.

cond-mat.mes-hall↗

arXiv2016

Optical patterning of trapped charge in nitrogen-doped diamond

The nitrogen-vacancy (NV) centre in diamond is emerging as a promising platform for solid-state quantum information processing and nanoscale metrology. Of interest in these applications is the manipulation of the NV charge, which can be attained by optical excitation. Here we use two-color optical microscopy to investigate the dynamics of NV photo-ionization, charge diffusion, and trapping in type-1b diamond. We combine fixed-point laser excitation and scanning fluorescence imaging to locally alter the concentration of negatively charged NVs, and to subsequently probe the corresponding redistribution of charge. We uncover the formation of spatial patterns of trapped charge, which we qualitatively reproduce via a model of the interplay between photo-excited carriers and atomic defects. Further, by using the NV as a probe, we map the relative fraction of positively charged nitrogen upon localized optical excitation. These observations may prove important to transporting quantum information between NVs or to developing three-dimensional, charge-based memories.

cond-mat.mes-hall↗