Temperature Dependent Photophysics of Single NV Centers in Diamond

We present a comprehensive study of the temperature and magnetic-field dependent photoluminescence (PL) of individual NV centers in diamond, spanning the temperature-range from cryogenic to ambient conditions. We directly observe the emergence of the NV's room-temperature effective excited state structure and provide a clear explanation for a previously poorly understood broad quenching of NV PL at intermediate temperatures around 50 K. We develop a model that quantitatively explains all of our findings, including the strong impact that strain has on the temperaturedependence of the NV's PL. These results complete our understanding of orbital averaging in the NV excited state and have significant implications for the fundamental understanding of the NV center and its applications in quantum sensing.Comment: 5 pages, 4 figures plus Supplementary Material. Questions and comments are welcome. arXiv admin note: text overlap with arXiv:2105.0807

Charge stability and charge-state-based spin readout of shallow nitrogen-vacancy centers in diamond

Spin-based applications of the negatively charged nitrogen-vacancy (NV) center in diamonds require efficient spin readout. One approach is the spin-to-charge conversion (SCC), relying on mapping the spin states onto the neutral (NV$^0$) and negative (NV$^-$) charge states followed by a subsequent charge readout. With high charge-state stability, SCC enables extended measurement times, increasing precision and minimizing noise in the readout compared to the commonly used fluorescence detection. Nano-scale sensing applications, however, require shallow NV centers within a few \si{\nano \meter} distance from the surface where surface related effects might degrade the NV charge state. In this article, we investigate the charge state initialization and stability of single NV centers implanted \approx \SI{5}{\nano \meter} below the surface of a flat diamond plate. We demonstrate the SCC protocol on four shallow NV centers suitable for nano-scale sensing, obtaining a reduced readout noise of 5--6 times the spin-projection noise limit. We investigate the general applicability of SCC for shallow NV centers and observe a correlation between NV charge-state stability and readout noise. Coating the diamond with glycerol improves both charge initialization and stability. Our results reveal the influence of the surface-related charge environment on the NV charge properties and motivate further investigations to functionalize the diamond surface with glycerol or other materials for charge-state stabilization and efficient spin-state readout of shallow NV centers suitable for nano-scale sensing.Comment: 9 pages, 5 figure

A Probabilistic Finite State Logic Machine Realized Experimentally on a Single Dopant Atom

Exploiting the potential of nanoscale devices for logic processing requires the implementation of computing functionalities departing from the conventional switching paradigm. We report on the design and the experimental realization of a probabilistic finite state machine in a single phosphorus donor atom placed in a silicon matrix electrically addressed and probed by scanning tunneling spectroscopy (STS). The single atom logic unit simulates the flow of -visitors in a maze whose topology is determined by the dynamics of the electronic transport through the states of the dopant. By considering the simplest case of a unique charge state for which three be resolved, we demonstrate an efficient solution of the following problem: in a maze of four connected rooms, what is the optimal combination of door opening rates in order to maximize the time that visitors spend in one specific chamber? The implementation takes advantage of the stochastic nature of electron tunneling, while the output remains the macroscopic current whose reading can be realized with standard techniques and does not require single electron sensitivity

Mn doped InSb studied at the atomic scale by cross-sectional scanning tunneling microscopy

We present an atomically resolved study of metal-organic vapor epitaxy grown Mn doped InSb. Both topographic and spectroscopic measurements have been performed by cross-sectional scanning tunneling microscopy (STM). The measurements on the Mn doped InSb samples show a perfect crystal structure without any precipitates and reveal that Mn acts as a shallow acceptor. The Mn concentration of the order of 1020cm3 obtained from the cross-sectional STM data compare well with the intended doping concentration. While the pair correlation function of the Mn atoms showed that their local distribution is uncorrelated beyond the STM resolution for observing individual dopants, disorder in the Mn ion location giving rise to percolation pathways is clearly noted. The amount of clustering that we see is thus as expected for a fully randomly disordered distribution of the Mn atoms and no enhanced clustering or second phase material was observed

Implementation of multivariable logic functions in parallel by electrical addressing a molecule of three dopants in Silicon

To realize low power compact logic circuits one can explore parallel operation on single nanoscale devices. An added incentive is to use multivalued (as distinct from Boolean) logic. Here we theoretically demonstrate that the computation of all the possible outputs of a multivariate, multivalued logic function can be implemented in parallel by electrical addressing of a molecule made up of three interacting dopant atoms embedded in Si. The electronic states of the dopant molecule are addressed by pulsing a gate voltage. By simulating the time evolution of the non stationary electronic density built by the gate voltage, we show that one can implement a molecular decision tree that provides in parallel all the outputs for all the inputs of the multivariate, multivalued logic function. The outputs are encoded in the populations and in the bond orders of the dopant molecule, which can be measured using a STM tip. We show that the implementation of the molecular logic tree is equivalent to a spectral function decomposition. The function that is evaluated can be field-programmed by changing the time profile of the pulsed gate voltage

Mn doped InSb studied at the atomic scale by cross-sectional scanning tunneling microscopy

We present an atomically resolved study of metal-organic vapor epitaxy grown Mn doped InSb. Both topographic and spectroscopic measurements have been performed by cross-sectional scanning tunneling microscopy (STM). The measurements on the Mn doped InSb samples show a perfect crystal structure without any precipitates and reveal that Mn acts as a shallow acceptor. The\u3cbr/\u3eMn concentration of the order of 1020cm3 obtained from the cross-sectional STM data compare well with the intended doping concentration. While the pair correlation function of the Mn atoms showed that their local distribution is uncorrelated beyond the STM resolution for observing individual dopants, disorder in the Mn ion location giving rise to percolation pathways is clearly noted. The amount of clustering that we see is thus as expected for a fully randomly disordered distribution of the Mn atoms and no enhanced clustering or second phase material was observed

Observation of the symmetry of core states of a single Fe impurity in GaAs

\u3cp\u3eWe report the direct observation of two mid-gap core d states of differing symmetry for a single Fe atom embedded in GaAs. These states are distinguished by the strength of their hybridization with the surrounding host electronic structure. The midgap state of Fe that does not hybridize via σ bonding is strongly localized to the Fe atom, whereas the other, which does, is extended and comparable in size to other acceptor states. Tight-binding calculations of these midgap states agree with the spatial structure of the measured wave functions and illustrate that such measurements can determine the degree of hybridization via π bonding of impurity d states. These single-dopant midgap states with strong d character, which are intrinsically spin-orbit-entangled, provide an opportunity for probing and manipulating local magnetism and may be of use for high-speed electrical control of single spins.\u3c/p\u3