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Functionalized Single-Atom-Embedded Bilayer Graphene and Hexagonal Boron Nitride
摘要： Single-atom-embedded bilayer graphene and two-dimensional hexagonal boron nitride are proposed in terms of first-principles calculations. In particular, a series of 68 different single atoms are embedded within bilayer graphene and boron nitride. It is revealed that the magnetic moment and bandgap behave differently depending on the atomic element used for doping where it becomes possible to form a magnet, conductor, semiconductor, or insulator. The electronic and geometrical properties of bilayer graphene and boron nitride are, in principle, able to be tailored and tuned, thereby expanding on how two-dimensional materials are functionalized and designed.
关键词： single atom,boron nitride,bandgap,graphene,functionalized graphene,magnetic moment
更新于2025-09-23 15:23:52
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Frequency shift of an optical cavity mode due to a single-atom motion
摘要： Using quantum coherence effects, we have developed a new technique of detection of motion of single atoms or ions in an optical cavity. We have theoretically demonstrated that the presence of a single atom or ion inside cavity leads to a shift in cavity frequency and phase of transmitted probe beams. It has been shown by the use of EIT technique, the change of the phase is extremely sensitive to probe detuning in the vicinity of resonance frequency and can be in the order of 10?4.
关键词： optical cavity,frequency shift,Single-atom detector,phase shift,quantum coherence
更新于2025-09-23 15:22:29
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European Microscopy Congress 2016: Proceedings || In-situ E(S)TEM Observations of Single Atom Dynamics in Catalytic Reactions
摘要： In heterogeneous catalysis, single-atom catalysts (SACs) take place at the atomic level at elevated temperatures. Understanding and control of complex catalytic reactions on the atomic scale are crucial for the rational development of improved catalysts and processes. The development of the first atomic-scale resolution environmental transmission electron microscopy (ETEM) is described (1-5), opening up new opportunities for studying gas-solid reactions in real time (6-9). The in-situ observations in ETEM have revealed the direct visualization of reaction intermediates and processes on the atomic scale in real time (1-5), offering insights into the dynamic behavior of catalysts and processes. The development of the ETEM (2) is now used globally. Benefits of the in-situ studies include new knowledge, improved and more environmentally beneficial catalytic technology as well as better or replacement mainstrain technologies in chemical and energy industries. Examples of the in-situ studies include new gold, improved and more environmentally beneficial catalytic technology as well as better or replacement mainstrain technologies in chemical and energy industries. The new insights have important implications for the application of nanomaterials in chemical process technologies including for transportation fuels, transformation fuels and in ammonia manufacture (6). Recently supported noble metal catalysts are examined for low temperature water-gas shift (WGS) catalysts (Fig. 1) and compared with reaction data and modeling. The in-situ observations in WGS have revealed the formation of clusters of only a few atoms from single-atom catalysts and the catalytic effect of low coordination sites. The new insights have important implications for the application of nanomaterials in chemical process technologies.
关键词： gas-solid reactions,environmental transmission electron microscopy,catalysis,single-atom catalysts,in-situ observations
更新于2025-09-23 15:22:29
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Optimal storage of a single photon by a single intra-cavity atom
摘要： We theoretically analyze the efficiency of a quantum memory for single photons. The photons propagate along a transmission line and impinge on one of the mirrors of a high-finesse cavity. The quantum memory is constituted by a single atom within the optical resonator. Photon storage is realized by the controlled transfer of the photonic excitation into a metastable state of the atom and occurs via a Raman transition with a suitably tailored laser pulse, which drives the atom. Our study is supported by numerical simulations, in which we include the modes of the transmission line and we use the experimental parameters of existing experimental setups. It reproduces the results derived using input–output theory in the corresponding regimes and can be extended to compute dynamics where the input–output formalism cannot be straightforwardly applied. Our analysis determines the maximal storage efficiency, namely, the maximal probability to store the photon in a stable atomic excitation, in the presence of spontaneous decay and cavity parasitic losses. It further delivers the form of the laser pulse that achieves the maximal efficiency by partially compensating parasitic losses. We numerically assess the conditions under which storage based on adiabatic dynamics is preferable to non-adiabatic pulses. Moreover, we systematically determine the shortest photon pulse that can be efficiently stored as a function of the system parameters.
关键词： single photon,three level system,storage efficiency,optical cavity,single atom,quantum memory
更新于2025-09-23 15:21:01
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Deep Learning Enabled Strain Mapping of Single-Atom Defects in 2D Transition Metal Dichalcogenides with Sub-picometer Precision
摘要： 2D materials offer an ideal platform to study the strain fields induced by individual atomic defects, yet challenges associated with radiation damage have so-far limited electron microscopy methods to probe these atomic-scale strain fields. Here, we demonstrate an approach to probe single-atom defects with sub-picometer precision in a monolayer 2D transition metal dichalcogenide, WSe2-2xTe2x. We utilize deep learning to mine large datasets of aberration-corrected scanning transmission electron microscopy images to locate and classify point defects. By combining hundreds of images of nominally identical defects, we generate high signal-to-noise class averages which allow us to measure 2D atomic spacings with up to 0.2 pm precision. Our methods reveal that Se vacancies introduce complex, oscillating strain fields in the WSe2-2xTe2x lattice that correspond to alternating rings of lattice expansion and contraction. These results indicate the potential impact of computer vision for the development of high-precision electron microscopy methods for beam-sensitive materials.
关键词： scanning transmission electron microscopy,strain mapping,single-atom defects,Deep learning,fully convolutional network (FCN),2D materials
更新于2025-09-23 15:21:01
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A Novel Single-Atom Electrocatalyst Ti <sub/>1</sub> /rGO for Efficient Cathodic Reduction in Hybrid Photovoltaics
摘要： Single-atom catalysts (SACs) are a frontier research topic in the catalysis community. Carbon materials decorated with atomically dispersed Ti are theoretically predicted with many attractive applications. However, such material has not been achieved so far. Herein, a Ti-based SAC, consisting of isolated Ti anchored by oxygen atoms on reduced graphene oxide (rGO) (termed as Ti1/rGO), is successfully synthesized. The structure of Ti1/rGO is characterized by high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption fine structure spectroscopy, being determined to have a five coordinated local structure TiO5. When serving as non-Pt cathode material in dye-sensitized solar cells (DSCs), Ti1/rGO exhibits high electrocatalytic activity toward the tri-iodide reduction reaction. The power conversion efficiency of DSCs based on Ti1/rGO is comparable to that using conventional Pt cathode. The unique structure of TiO5 moieties and the crucial role of atomically dispersed Ti in Ti1/rGO are well understood by experiments and density functional theory calculations. This emerging material shows potential applications in energy conversion and storage devices.
关键词： reduced graphene oxide,titanium,single-atom catalysts,dye-sensitized solar cells,cathode reaction
更新于2025-09-23 15:21:01
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Quantum Squeezing of the Field of a Single-Atom Laser under Conditions of a Variable Coupling Constant
摘要： A nonstationary regime of squeezed-light generation by a single-atom laser is investigated. Dependences of the quantum-squeezing parameter and radiation intensity on modulation frequency of the atom–field coupling constant are obtained. It is demonstrated that a resonance appears at the modulation frequency equal to twice the average coupling constant, which leads to a more efficient quantum squeezing in a nonstationary harmonic regime than in the case of a stationary regime for the same values of the relaxation and pump parameters.
关键词： single-atom laser,coupling constant,squeezed light
更新于2025-09-19 17:13:59
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Single atom laser in normal-superconductor quantum dots
摘要： We study a single-level quantum dot strongly coupled to a superconducting lead and tunnel coupled to a normal electrode which can exchange energy with a single-mode resonator. We show that such a system implements a single atom laser. We employ both a semiclassical treatment and a quantum master-equation approach to characterize the properties of this laser. In particular, we ?nd that this system can be operated with ef?ciency approaching unity; that is, a single photon is emitted into the cavity for every Cooper pair participating in the charge current. We ?nd also that lasing in the proposed setup is clearly identi?able in the transport properties: in the lasing state, the electrical current through the quantum dot is pinned to the maximum value achievable in this hybrid nanostructure, and hence, the onset of lasing can be detected simply by a current measurement.
关键词： semiclassical treatment,quantum dot,Cooper pair,transport properties,superconducting lead,charge current,single atom laser,quantum master-equation approach,single-mode resonator,normal electrode
更新于2025-09-12 10:27:22
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Discrete exited states influence on the harmonics spectrum generated in two-colour laser fields
摘要： The contribution of excited discrete atomic levels to the generation of high- and low-order harmonics in the interaction of a single atom with a two-color laser field has been studied for the first time. The studies were carried out for two types of atoms with different symmetry of the ground state wave functions (Ag, Ne) and for a two-color laser field consisting of the linearly polarized fundamental and second harmonics of Ti:Sa laser (ω + 2ω). The angle between the polarization of the ω + 2ω laser field components is varied. A significant effect of the symmetry of populated excited levels on the polarization characteristics of the generated harmonics is shown. A new method of control over the polarization state of the generated radiation is proposed.
关键词： non-perturbative theory,high harmonics generation,single atom response
更新于2025-09-12 10:27:22
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Single-Atomically Anchored Cobalt on Carbon Quantum Dots as Efficient Photocatalysts for Visible Light-promoted Oxidation Reactions
摘要： Generation of efficient light-induced charge separation inside the photocatalyst is an essential factor for a high catalytic efficiency. The usual immobilization of metal or metal oxide particles on semiconductor photocatalysts offers an uncontrolled assembly of active sites during the reaction. The introduction of single metal atoms on photocatalysts can lead to extremely high atomic utilization and precise active sites. However, this approach is limited due to the lack of suitable photosensitizers for single atom immobilization. Here, we have designed photocatalytic carbon quantum dots with anchoring sites for single cobalt atoms in a defined Co-N4 structure via facile pyrolysis of vitamin B12. Carbon dots functioned as both light-harvesting antenna and support for cobalt atom with high atom loadings up to 3.27 wt.%. This new photocatalytic material demonstrated enhanced visible light absorption, efficient charge separation, and reduced electrochemical impedance, while the single Co atoms acted as the active site with strong oxidative ability. As a result, the photocatalysts showed excellent visible light-promoted photocatalytic efficiency with oxygen evolution rates up to 168 μmol h-1 g-1 via water oxidation, imine formation with high conversion (~90%) and selectivity (>99%), and complete photodegradation of organic dyes.
关键词： single-atom catalysts,oxidation reactions,carbon quantum dots,photocatalysis,visible light
更新于2025-09-12 10:27:22