Scanning nitrogen-vacancy (NV) center electrometry has shown potential for quantitative quantum imaging of electric fields at the nanoscale. However, achieving nanoscale spatial resolution remains a challenge since employing gradiometry to overcome electrostatic screening causes resolution-limiting trade-offs including the averaging effect and the sensor-sample proximity. Here, we demonstrate a scanning NV center protocol that achieves an enhanced spatial resolution of ∼10 nm. We develop an axially symmetric probe with a sub-nanometer oscillating amplitude, which simultaneously provides robust intermittent-contact mode feedback and ensures close engagement between the diamond tip and the sample. As an example, we experimentally demonstrate a 10 nm spatial resolution on ferroelectric lithium niobate. Scanning NV center electrometry with this resolution can directly resolve the nanoscale polar textures and dynamics of emerging ferroelectrics, which commonly arise on the scale of tens of nanometers.

Magnetic skyrmions are localized magnetic structures that retain their shape and stability over time, thanks to their topological nature. Recent theoretical and experimental progress has laid the groundwork for understanding magnetic skyrmions characterized by negligible net magnetization and ultrafast dynamics. Notably, skyrmions emerging in materials with altermagnetism, a novel magnetic phase featuring lifted Kramers degeneracy-have remained unreported until now. In this study, we demonstrate that BiFeO3, a multiferroic renowned for its strong coupling between ferroelectricity and magnetism, can transit from a spin cycloid to a Neel-type skyrmion under antidamping spin-orbit torque at room temperature. Strikingly, the altermagnetic spin splitting within BiFeO3 skyrmion can be reversed through the application of an electric field, revealed via the Circular photogalvanic effect. This quasiparticle, which possesses a neutral topological charge, holds substantial promise for diverse applications-most notably, enabling the development of unconventional computing systems with low power consumption and magnetoelectric controllability.

Solid-state spins in diamond are promising building blocks for quantum computing and quantum sensing, both of which require precise nanoscale addressing of individual spins. To explore the resolution limit of this approach, we demonstrate Fourier magnetic imaging of nitrogen-vacancy centers in diamond under state-of-the-art conditions. We constructed a highly compact experimental platform featuring thermal drift compensation under ambient conditions and generated a pulsed magnetic field gradient of up to 13.5 G/μm. By implementing the Fourier magnetic imaging protocol, we achieved localization of a single nitrogen-vacancy center with a spatial resolution of 0.28 ± 0.10 nm and a magnetic field measurement deviation of 9 nT. This technique holds potential for applications such as localizing spins within proteins and cells.

Solid-state spins in diamond are promising building blocks for quantum computing and quantum sensing, both of which require precise nanoscale addressing of individual spins. To explore the resolution limit of this approach, we demonstrate Fourier magnetic imaging of nitrogen-vacancy (NV) centers in diamond under state-of-the-art conditions. We constructed a highly compact experimental platform featuring thermal drift compensation under ambient conditions and generated a pulsed magnetic field gradient of up to 13.5 G/mu m. By implementing the Fourier magnetic imaging protocol, we achieved localization of a single NV center with a pixel resolution of 0.69 nm and a magnetic field measurement deviation of 9 nT. This technique holds potential for applications such as localizing spins within proteins and cells.

In order to distinguish the interaction responses between unsteady thermal waves and thermal diffusion in graphene, the relaxation time of the heat flux vector Tq and the relaxation time of the temperature gradient TT are introduced based on the Fourier's law, and a two-phase relaxation theoretical model is established. Using parameter B, which describes the ratio of relaxation times between two phases, to reveal the influence of the interaction between thermal waves and thermal diffusion and to investigate the regulation mechanism of heat transport modes. When B approaches zero, the thermal wave effect dominates the heat transfer. When B approaches 0.5, the thermal diffusion characteristics are significant. When B is between zero and 0.5, both of them jointly dominate the heat transfer, and the interaction between the two is of great significance. The results uncover the rules of thermal diffusion induced wave attenuation and thermal wave promoted thermal diffusion. They exhibit strong coupling characteristics. The unique contribution of third-order partial derivatives to local thermal wave disturbances is also revealed. A molecular dynamics model of short-pulse thermal shock for zigzag graphene is developed to reveal the coupling behaviors between thermal waves and thermal diffusion. The calculation parameters of the two-phase relaxation theoretical model are calibrated. The temperature field following the second sound is the outcome of the combined action of thermal waves and thermal diffusion. It is worth noting that except for the out-of-plane thermal wave, which has a higher speed than the out-of-plane transverse elastic wave, the speeds of the other two thermal waves are both lower than their corresponding elastic wave velocities. The above results indicate that the two-phase relaxation model can accurately depict the non-equilibrium thermal behaviors of micro-and nano-scale devices and can provide a theoretical basis for protecting micro-components in integrated circuits against thermal radiation and thermal diffusion.

Frequency multiplication involves generating harmonics from an input frequency, a technique particularly useful for integrating spin-wave devices operating at different frequencies. While topological magnetic textures offer distinct advantages in spin-wave applications, frequency multiplication has not yet been observed in these structures. Here, we study the magnetization dynamics of magnetic vortices formed in micron-sized disks via wide-field magnetic imaging. We found the occurrence of coherent spin-wave harmonics arising from the gyration of vortex cores driven by microwave fields. This phenomenon reveals a universal mechanism where the periodical motion of delta function-like objects such as vortex cores gives rise to a frequency comb. Our results pave the way for creating nanoscale, tunable spin-based frequency multipliers and open new possibilities for developing miniature frequency combs in a variety of systems.

Advances in hybrid quantum systems and their precise control are pivotal for developing advanced quantum technologies. Two-dimensional (2D) materials with optically accessible spin defects have emerged as a promising platform for building integrated quantum spin systems due to their exceptional flexibility and scalability. However, experimentally realizing such systems and demonstrating their superiority remains challenging. Here, we present a hybrid spin system operating under ambient conditions, integrating boron vacancy ( V_B^- ) spins in 2D hexagonal boron nitride flakes with a single nitrogen vacancy (NV) center in 3D single-crystal diamonds. This combined system achieves full controllability and exhibits enhanced performance for nanoscale magnetic sensing, including an improved dynamic range. Moreover, we investigate the rich many-body spin dynamics within the hybrid system, which enables us to estimate the concentration of V_B^- spins. This work provides a critical foundation for advancing the development of 2D-3D integrated quantum spin systems.

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.

Ensemble nitrogen-vacancy (NV) centers in diamond are promising platforms for quantum sensing due to their exceptional magnetic sensitivity. This sensitivity is critically governed by the NV ensemble's yield, which determines the number of active sensors and their coherence properties. A high yield is essential for simultaneously achieving a high NV density and long spin coherence time. However, the complex process of NV formation remains quantitatively poorly understood. In this study, we systematically optimize the electron irradiation dose to maximize the yield of NV ensembles in chemical vapor deposition (CVD) diamond. We quantitatively characterize the concentrations of key nitrogen-related defects, including vacancies and electron donors, under varying conditions. Our results identify the initial P1 center (nitrogen) concentration, the vacancy yield, and the availability of electron donors as the primary factors controlling the final NV yield. These findings provide crucial insights for defect engineering strategies to enhance NV center production, paving the way for more sensitive and efficient quantum sensors.

Critical fluctuations play a crucial role in determining spin orders in low-dimensional magnetic materials. However, experimentally linking these fluctuations to scaling theory-and thereby uncovering insights into spin interaction models-remains a challenge. Here, we utilize a nitrogen-vacancy center-based quantum decoherence imaging technique to probe critical fluctuations in the van der Waals magnet Fe3GeTe2. Our data reveal that critical fluctuations produce a random magnetic field, with noise spectra undergoing significant changes near the critical temperature. To explain this phenomenon, we developed a theoretical framework showing that the spectral density exhibits 1/f noise characteristics near the critical temperature, transitioning to white noise behavior away from this regime. By experimentally adjusting the sample-to-diamond distance, we identified the crossover temperature between these two noise types. These findings offer an approach to studying phase transition dynamics through critical fluctuations, enabling precise determination of critical exponents associated with long-range correlations. This methodology holds promise for advancing our understanding of critical phenomena across diverse physical systems.

Quantum coherence serves as a crucial quantum resource for achieving high-sensitivity quantum sensing. Because of its long coherence time at room temperature, the nitrogen-vacancy (NV) center has emerged as a quantum sensor in various fields in recent years. While nanoscale quantum sensing at room temperature has been demonstrated for NV centers, noise on the diamond surface severely limits its further development at a higher sensitivity. Here, we utilize the hybridization between graphene and diamond surfaces to directly deplete surface unpaired electron spins, thereby achieving roughly two-fold enhancement in coherence. Through the combination of electron spin resonance spectra and first-principle calculations, we explain that this phenomenon arises from a significant reduction in electron spin density on the diamond surface due to interface electron orbital hybridization. Our research presents a new approach for solid-state quantum sensors to reach the desired sensitivity level and offers a new pathway for future studies on material interfaces.

Two-dimensional heterojunctions provide a versatile platform for exploring various quantum properties. Here, we create bilayer 1T/2H-NbSe2 heterophase junctions and realize two types of stacking configurations with picometer-level lattice shifts. By high-resolution scanning tunneling microscopy/spectroscopy, we found that the electronic states are highly dependent on the stacking configurations of the 1T layer on the 2H one. Unexpectedly, a tiny shift between the two configurations (about 110 pm in the lateral direction and 30 pm in the vertical one) leads to a change from a correlated gap lattice into a Kondo peak lattice. Moreover, both of them show a spin-related pseudogap width of 2-3 meV close to the Fermi level, which splits under the external magnetic field. Our study demonstrates the important role of delicate stacking configurations on the many-body physics and spin-related phenomena in the heterophase junctions.

The nitrogen-vacancy center in diamond serves as a nanoscale multi-sensor for precise magnetic and electric field measurements in optically detected magnetic resonance (ODMR) experiments. The ODMR system at cryogenic temperatures can be employed for the exploration of significant physical phenomena, such as two-dimensional ferromagnetism and current transport dynamics. Conventional systems, however, suffer from limited scanning range, low load capacity, and instability due to their reliance on cryogenic scanning mechanisms to manipulate samples, objective, and magnetic components. Here, we present a cryogenic ODMR platform utilizing all room-temperature scanning systems, enabling stable operation from 300 to 10.6 K. Our design achieves a positioner motion range of >5 cm and makes it possible to range from 50 to 5000 G, addressing critical challenges in applications requiring large-scale magnetic field scanning and broad temperature range experiments, such as quantum relaxometry studies. The system exhibits high robustness (vibrations <50 nm), high load capacity, cost-effectiveness, and ease of maintenance. Furthermore, our approach can also be directly applied to other promising quantum bit platforms, such as solid-state spin defects in silicon carbide (SiC) and so on.

Ceramics are usually obtained by powder sintering at a temperature higher than 1000 degrees C. By contrast, living organisms can use hydrated amorphous precursors to produce biominerals with high inorganic content and excellent mechanical properties under mild conditions. Here, inspired by the biomineralization process, aragonite ceramic composed of densely packed nanocrystals is manufactured by in situ crystallization and densification of amorphous calcium carbonate (ACC) under pressure at low temperature (80 degrees C). It is demonstrated that the structural water played critical roles in promoting the fusion of nanoparticles, nucleation of aragonite nanocrystals, and further densification. More importantly, strong nacre-like aragonite ceramic is constructed by introducing cellulose films as the organic layers, where a gradient interface is achieved by water-promoted fusion of nanocrystals into cellulose. Notably, the hardness and Young's modulus of the artificial nacre from nanoindentation can reach 3.76 and 63.38 GPa, respectively, which are comparable to natural nacre. The macroscopic mechanical analysis gave a Vickers hardness of 258.26 Kgf mm-2 and Young's modulus of 5.94 GPa. Besides, the flexural strength and fracture toughness can reach 158.0 MPa and 3.35 MPa m1/2, respectively. Thus, the study provides a new bioprocessing-inspired strategy for the fabrication of ceramics with excellent mechanical properties at low temperatures.

The application of the vector magnetometry based on nitrogen-vacancy（NV） ensembles has been widely investigated in multiple areas.It has the superiority of high sensitivity and high stability in ambient conditions with microscale spatial resolution.However,a bias magnetic field is necessary to fully separate the resonance lines of optically detected magnetic resonance（ODMR） spectrum of NV ensembles.This brings disturbances in samples being detected and limits the range of application.Here,we demonstrate a method of vector magnetometry in zero bias magnetic field using NV ensembles.By utilizing the anisotropy property of fluorescence excited from NV centers,we analyzed the ODMR spectrum of NV ensembles under various polarized angles of excitation laser in zero bias magnetic field with a quantitative numerical model and reconstructed the magnetic field vector.The minimum magnetic field modulus that can be resolved accurately is down to ～0.64 G theoretically depending on the ODMR spectral line width（1.8 MHz）,and ～2 G experimentally due to noises in fluorescence signals and errors in calibration.By using 13 C purified and low nitrogen concentration diamond combined with improving calibration of unknown parameters,the ODMR spectral line width can be further decreased below 0.5 MHz,corresponding to ～0.18 G minimum resolvable magnetic field modulus.

It is of great significance to investigate the dynamic responses of functionally graded materials (FGMs). A series of experiments are conducted to evaluate the dynamic behaviors of the laminated and graded ZrC-Mo composites with three graded exponents (i.e., 0.69, 1.35, and 2.70) by the split Hopkinson pressure bar (SHPB) device. The graded composites with an exponent of 0.69 show the highest strength and best performances of the three. It results from the formation of local stress-transferring structures and the interaction of the ZrC component and Mo component. Based on the digital imaging correlation (DIC) method, different evolutions of local strains in the ZrC-rich and the Mo-rich regions are analyzed by changing the gradient directions of the composites. The transmission behaviors of stress waves in the laminated and graded composite with multi-interfaces are investigated theoretically. The finite element method (FEM) is used to evaluate influences of the plasticity of metal component, and the transmitted coefficient in theory is employed to optimize and evaluate the laminated and graded structures. It also indicates the special role of loading frequency. These results might be helpful for a profound understanding of the internal wave propagation and guide the structural designing optimization.

A nitrogen-vacancy center based scanning magnetic microscope can be used to characterize magnetics at the nanoscale with high sensitivity. This paper reports a field-programmable-gate-array based hardware system that is designed to realize control and signal readout for fast scanning magnetic imaging with a nitrogen-vacancy center. A 10-channel 1 Msps @ 20 bit analog signal generator, a 12-channel 50 ps resolution pulse generator, a 300 Msps @ 16 bit lock-in amplifier with proportional integral derivative control function, and a 4-channel 200 Msps counter are integrated on the platform. A customized acceleration algorithm is realized with the re-configurable field-programmable-gate-array chip to accelerate the imaging speed of the nitrogen-vacancy system, and the experimental results prove that the imaging efficiency can be accelerated by five times compared to the system without the acceleration algorithm. The platform has considerable potential for future applications of fast scanning magnetic imaging.

Nitrogen vacancy (NV) color centers in diamond have useful applications in quantum sensing and fluorescent marking. They can be generated experimentally by ion implantation, femtosecond lasers, and chemical vapor deposition. However, there is a lack of studies of the yield of NV color centers at the atomic scale. In the molecular dynamics simulations described in this paper, NV color centers are prepared by ion implantation in diamond with pre-doped nitrogen and subsequent annealing. The differences between the yields of NV color centers produced by implantation of carbon (C) and nitrogen (N) ions, respectively, are investigated. It is found that C-ion implantation gives a greater yield of NV color centers and superior location accuracy. The effects of different pre-doping concentrations (400–1500 ppm) and implantation energies (1.0–3.0 keV) on the NV color center yield are analyzed, and it is shown that a pre-doping concentration of 1000 ppm with 2 keV C-ion implantation can produce a 13% yield of NV color centers after 1600 K annealing for 7.4 ns. Finally, a brief comparison of the NV color center identification methods is presented, and it is found that the error rate of an analysis utilizing the identify diamond structure + coordination analysis method is reduced by about 7% compared with conventional identification methods.

Wide-field magnetic imaging based on nitrogen-vacancy (NV) centers in diamond has been shown the applicability in material and biological science. However, the spatial resolution is limited by the optical diffraction limit (>200 nm) due to the optical real-space localization and readout of NV centers. Here, we report the wide-field Fourier magnetic imaging technique to improve spatial resolution beyond the optical diffraction limit while maintaining the large field of view. Our method relies on wide-field pulsed magnetic field gradient encoding of NV spins and Fourier transform under pixel-dependent spatial filters. We have improved spatial resolution by a factor of 20 compared to the optical resolution and demonstrated the wide-field super-resolution magnetic imaging of a gradient magnetic field. This technique paves a way for efficient magnetic imaging of large-scale fine structures at the nanoscale.