Electron paramagnetic resonance spectroscopy (EPR) is among the most important analytical tools in physics, chemistry, and biology. The emergence of nitrogen-vacancy (NV) centers in diamond, serving as an atomic-sized magnetometer, has promoted this technique to single-spin level, even under ambient conditions. Despite the enormous progress in spatial resolution, the current megahertz spectral resolution is still insufficient to resolve key heterogeneous molecular information. A major challenge is the short coherence times of the sample electron spins. Here, we address this challenge by employing a magnetic noise-insensitive transition between states of different symmetry. We demonstrate a 27-fold narrower spectrum of single substitutional nitrogen (P1) centers in diamond with linewidth of several kilohertz, and then some weak couplings can be resolved. Those results show both spatial and spectral advances of NV center-based EPR, and provide a route towards analytical (EPR) spectroscopy at single-molecule level.
Recent experiments have demonstrated Rabi-oscillations, superradiant pulses and stimulated emission from negatively-charged nitrogen-vacancy ($\mathrm{NV}^{-}$) center spins in microwave resonators. These phenomena witness the kind of collective and strong coupling which has been prerequisite for observation of superradiant lasing in the optical frequency regime. In this article, we investigate the possibility to employ coherence, present in both the collective $\mathrm{NV}^{-}$ spin ensemble and the microwave field, to achieve a superradiant maser. Our calculations show that a superradiant ma…
In this work we use fluorescence from nitrogen-vacancy defects in diamond to detect and explore other paramagnetic defects in the diamond, such as P1 defects, which are commonly undetectable through optical detection of magnetic resonance in standard conditions. Our method does not require overlap between the defects' resonances and therefore is applicable in a wide region of magnetic fields and frequencies, as verified by excellent fit to theoretical predictions. We propose a depolarization scheme of P1 defects to account for the observed data. To verify our results, we perform cavity-based d…
The electronic spins of the nitrogen-vacancy centers (NV centers) in Chemical-Vapor-Deposition (CVD) grown diamonds form ideal probes of magnetic fields and temperature, as well as promising qu-bits for quantum information processing. Studying and controlling the magnetic environment of NV centers in such high purity crystals is thus essential for these applications. We demonstrate optical detection of paramagnetic species, such as hydrogen-related complexes, in a CVD-grown diamond. The resonant transfer of the NV centers' polarized electronic spins to the electronic spins of these species gen…
Spin waves have risen as promising candidate information carriers for the next generation of information technologies. Recent experimental demonstrations of their detection using electron spins in diamond pave the way towards studying the back-action of a controllable paramagnetic spin bath on the spin waves. Here, we present a quantum theory describing the interaction between spin waves and paramagnetic spins. As a case study we consider an ensemble of nitrogen-vacancy spins in diamond in the vicinity of an Yttrium-Iron-Garnet thin film. We show how the back-action of the ensemble results in …
We report a study of the magnetic field dependence of photoluminescence of NV$^-$ centers (negatively charged nitrogen-vacancy centers) in diamond single crystals. In such a magnetic field dependence characteristic sharp features are observed, which are coming from Level Anti-Crossings (LACs) in a coupled electron-nuclear spin system. For sensitive detection of such LAC-lines we use lock-in detection to measure the photoluminescence intensity. This experimental technique allows us to obtain new LAC lines. Additionally, a remarkably strong dependence of the LAC-lines on the modulation frequency…
Color-center-hosting semiconductors are emerging as promising source materials for low-field dynamic nuclear polarization (DNP) at or near room temperature, but hyperfine broadening, susceptibility to magnetic field heterogeneity, and nuclear spin relaxation induced by other paramagnetic defects set practical constraints difficult to circumvent. Here, we explore an alternate route to color-center-assisted DNP using nitrogen-vacancy (NV) centers in diamond coupled to substitutional nitrogen impurities, the so-called P1 centers. Working near the level anti-crossing condition - where the P1 Zeema…
Optically-pumped color centers in semiconductor powders can potentially induce high levels of nuclear spin polarization in surrounding solids or fluids at or near ambient conditions, but complications stemming from the random orientation of the particles and the presence of unpolarized paramagnetic defects hinder the flow of polarization beyond the defect's host material. Here, we theoretically study the spin dynamics of interacting nitrogen-vacancy (NV) and substitutional nitrogen (P1) centers in diamond to show that outside protons spin-polarize efficiently upon a magnetic field sweep across…
We use tunable dipolar-interactions between the spins of nitrogen-vacancy (NV) centers in diamond to rotate a diamond crystal. Specifically, we employ cross-relaxation between the electronic spin of pairs of NV centers in a trapped diamond to enhance the anisotropic NV paramagnetism and thus to increase the associated spin torque. Our observations open a path towards the use of mechanical oscillators to detect paramagnetic defects that lack optical transitions, to investigation of angular momentum conservation in spin relaxation processes and to novel means of cooling the motion of mechanical …
Wide field-of-view magnetic field microscopy has been realised by probing shifts in optically detected magnetic resonance (ODMR) spectrum of Nitrogen Vacancy (NV) defect centers in diamond. However, these widefield diamond NV magnetometers require few to several minutes of acquisition to get a single magnetic field image, rendering the technique temporally static in it's current form. This limitation prevents application of diamond NV magnetometers to novel imaging of dynamically varying microscale magnetic field processes. Here, we show that the magnetic field imaging frame rate can be signif…
Single substitutional nitrogen atoms N$_s^0$ are the prerequisite to create nitrogen-vacancy (NV) centers in diamonds. They serve as the electron donors to create the desired NV$^-$ center, provide charge stability against photo-ionisation, but also are the main source of decoherence. Therefore, precise and quick determination of N$_s^0$ concentration is a key advantage to a multitude of NV-related research in terms of material improvement as well as applications. Here we present a method to determine the N$_s^0$ concentration based on absorption spectroscopy in the UV-Visible range and fittin…
The negatively charged nitrogen-vacancy (NV) center in nano- or micro- diamonds has emerged as a promising magnetic field sensor, as a candidate for hyper-polarizing paramagnetic species, as well as a tool for spin-mechanics at the nanoscale. However, NV-doped diamonds are presently not straightforwardly employable for these applications in a liquid or when levitating under atmospheric pressures due to the random angular Brownian motion which tends to rotate the NV quantization axis over the course of the measurments. Here, we report on angle locking of the crystalline axis of a trapped micro-…
Precision magnetometry is fundamental to the development of novel magnetic materials and devices. Recently, the nitrogen-vacancy (NV) center in diamond has emerged as a promising probe for static magnetism in 2D van der Waals materials, capable of quantitative imaging with nanoscale spatial resolution. However, the dynamic character of magnetism, crucial for understanding the magnetic phase transition and achieving technological applications, has rarely been experimentally accessible in single 2D crystals. Here, we coherently control the NV center's spin precession to achieve ultra-sensitive, …
Materials and Spin Characteristics of Nanodiamonds Partially Covered with Amino Groups and Embedded with Nitrogen-Vacancy Color Centers
HUN-REN Wigner Research Centre for Physics（匈牙利科学院维格纳物理研究中心）；Budapest University of Technology and Economics（布达佩斯技术与经济大学）；Institute of Technical Physics and Materials Science, HUN-REN Centre for Energy Research（匈牙利科学院能源研究中心技术物理与材料科学研究所）
We present an alternative to conventional Electron Paramagnetic Resonance (EPR) spectroscopy equipment. Avoiding the use of bulky magnets and magnetron equipment, we use the photoluminescence of an ensemble of Nitrogen-Vacancy centers at the surface of a diamond. Monitoring their relaxation time (or T1), we detected their cross-relaxation with a compound of interest. In addition, the EPR spectra are encoded through a localized magnetic field gradient. While recording previous data took 12 minutes per data point with individual NV centers, we were able to reconstruct a full spectrum at once in …
High-Field EPR/ENDOR of N/Be Centers for Defect Engineering in 6H-SiC
Institute of Physics, Kazan Federal University（喀山联邦大学物理研究所）；Ioffe Institute（约费研究所）；Higher School of Cybertechnology, Mathematics and Statistics, Plekhanov Russian University of Economics（普列汉诺夫俄罗斯经济大学网络技术与数学统计高等学院）
Owing to the unique electronic spin properties, the nitrogen-vacancy (NV) centers hosted in diamond have emerged as a powerful quantum sensor for various physical parameters and biological species. In this work, a miniature optical-fiber quantum probe, configured by chemically-modifying nanodiamonds NV centers on the surface of a cone fiber tip, is developed. Based on continue-wave optically detected magnetic resonance method and lock-in amplifying technique, it is found that the sensing performance of the probe can be engineered by varying the nanodiamonds dispersion concentration and modific…
Nitrogen-vacancy (NV) center in diamond is an ideal candidate for quantum sensors because of its excellent optical and coherence property. However, previous studies are usually conducted at low or room temperature. The lack of full knowledge of coherence properties of the NV center at high temperature limits NV's further applications. Here, we systematically explore the coherence properties of the NV center ensemble at temperatures from 300 K to 600 K. Coherence time $T_2$ decreases rapidly from $184 μs$ at 300 K to $30 μs$ at 600 K, which is attributed to the interaction with paramagnetic imp…
Isotropic Nanoscale Quantum Sensor at Room-Temperature
Leipzig University（莱比锡大学）；Felix-Bloch Institute for Solid State Physics, Leipzig University（莱比锡大学菲利克斯·布洛赫固体物理研究所）；Leibniz Institute of Surface Engineering（莱布尼茨表面工程研究所）
Dynamic nuclear polarization via contact with electronic spins has emerged as an attractive route to enhance the sensitivity of nuclear magnetic resonance (NMR) beyond the traditional limits imposed by magnetic field strength and temperature. Among the various alternative implementations, the use of nitrogen vacancy (NV) centers in diamond - a paramagnetic point defect whose spin can be optically polarized at room temperature - has attracted widespread attention, but applications have been hampered by the need to align the NV axis with the external magnetic field. Here we overcome this hurdle …
