The one-dimensional side gate based on graphene edges shows a significant capability of reducing the channel length of field-effect transistors, further increasing the integration density of semiconductor devices. The nanoscale electric field distribution near the edge provides the physical limit of the effective channel length; however, its imaging under ambient conditions is still lacking, which is a critical aspect for the practical deployment of semiconductor devices. Here, we used scanning nitrogen-vacancy (N-V) microscopy to investigate the electric field distribution near edges of single-layer graphene. Realspace scanning maps of photocharged floating graphene flakes were acquired with a spatial resolution of approximately 10 nm, and the electric edge effect was quantitatively studied by analyzing the N-V spin energy-level shifts due to the electric Stark effect. Since the graphene flakes are isolated from external electric sources, we brought out a theory based on the photothermionic effect to explain the charge transfer from graphene to the oxygen-terminated diamond probe with a disordered distribution of charge traps. Real-time tracing of electric fields detected the photothermionic emission process and the recombination process of the emitted electrons. This study provides a perspective for graphene-based one-dimensional gates and optoelectronics with nanoscale real-space imaging and, moreover, offers a method to tune the chemical environment of diamond surfaces based on optical charge transfer.

Nanoscale amplitude and phase sensing of a rf electromagnetic field can benefit broad frontiers in sci-ence and technology. The imaging applications in these research areas demand a nanoscale sensor able to detect rf electric fields over a wide frequency range under ambient conditions, which remains a challenge. Here, we present a rf electrometry based on the forbidden magnetic dipole transition of a single shallow nitrogen-vacancy center in diamond and experimentally demonstrate the detection of rf electric fields at frequencies ranging from 13.85 MHz to 2.02 GHz. A sensitivity of 265 V cm-1 Hz-1/2 for amplitude mea-surement and a standard deviation of 0.2 degrees for phase measurement are achieved. The potential applications of nanoscale sensing and imaging of electromagnetic field are discussed.

The nitrogen-vacancy (NV) color center quantum system in diamond has shown great application potential in the fields of solid-state quantum computing and quantum precision measurement because of its unique advantages such as single-spin addressing and manipulation and long quantum coherence time at room temperature. The precise manipulation technology of single spin is particularly important for the development of the application of NV center. The common spin manipulation methods used in NV center quantum system are to drive and manipulate the electron spin by resonant alternating magnetic field. In recent years, the electrical control of quantum spin has attracted extensive attention. In this paper, using the alternating electric field to control the electron spin of NV center is studied. The alternating electric field generated by the electrode successfully drives the Rabi oscillation of the NV center spin between the \begin{document}$\Delta m_{\rm{s}}=\pm2$\end{document} magnetic-dipole forbidden energy levels of \begin{document}$|m_{\rm{s}}=-1\rangle$\end{document} and \begin{document}$|m_{\rm{s}}=+1\rangle$\end{document}. Further studies show that the frequency of the electrically driven Rabi oscillation is controlled by the power of the driven electric field but independent of the resonant frequency of the electric field. The combination of spin electric control and magnetic control technology can realize the full manipulation of the direct transition among the three spin energy levels of NV center, thus promoting the development of the researches and applications of NV quantum system in the fields of quantum simulation, quantum computing, precision measurement of electromagnetic field, etc.

Ferromagnets with uniaxial magnetocrystalline anisotropy have been a significant platform to explore applications in magnetic devices. Although it is commonly recognized that the magnetic anisotropy is crucial for the formation of noncollinear domain patterns, the effects of the anisotropy direction are usually neglected in recent studies. Here, we imaged stray fields generated by a polycrystalline MnNiGa sample with a nitrogen-vacancy color center in diamond and found that various stripe domains and magnetic bubbles exist in different regions. These domain patterns could be explained by the difference in anisotropy directions among crystallites via micromagnetic simulation. It can be inferred that the magnetic anisotropy direction plays a key role in energetically favorable domain structures based on our results. The magnetic anisotropy direction may be exploited as an ingredient to modulate domains and develop devices.

The nitrogen-vacancy (NV) center is a potential atomic-scale spin sensor for electric field sensing. However, its natural susceptibility to the magnetic field hinders effective detection of the electric field. Here we propose a robust electrometric method utilizing continuous dynamic decoupling (CDD) technique. During the CDD period, the NV center evolves in a dressed frame, where the sensor is resistant to magnetic fields but remains sensitive to electric fields. As an example, we use this method to isolate the electric noise from a complex electromagnetic environment near diamond surface via measuring the dephasing rate between dressed states. By reducing the surface electric noise with different covered liquids, we observe an unambiguous relation between the dephasing rate and the relative dielectric permittivity of the liquid, which enables a quantitative investigation of electric noise model near the diamond surface.

Microwave magnetometry is essential to a variety of modern electronic techniques, most notably integrated circuits. The nitrogen-vacancy center in diamond has shown the ability of nanoscale resolution for the microwave magnetic field measurement and imaging. However, the characterization of the wideband magnetic field remains a challenge. Here we experimentally demonstrated a wideband microwave magnetometry with an off-resonance protocol based on the Bloch-Siegert shift effect. The off-resonance microwave magnetic field shifts the energy level of the nitrogen-vacancy center. It results in a phase accumulation during the evolution of the superposition state of the quantum sensor. According to this effect, by optimizing the evolution time, we experimentally verified the bandwidth widening of an order of magnitude compared with the Rabi oscillation, i.e., on-resonance method with an acceptable decrease of the sensitivity. In addition, we extracted themicrowave frequency with a two-qubit system, which consists of a nitrogen-vacancy center and a nearby C-13 nucleus. This approach enables the building of a wideband and potentially nanoscale microwave magnetometry to allow various potential applications, such as electronic circuits development.