In a paper published in the journal Nature Reviews Physics, researchers highlighted how nitrogen-vacancy (NV) centre quantum sensors advanced condensed matter studies by enabling quantitative, non-invasive, and nanoscale resolution measurements across varying temperatures.
Study: Nanoscale diamond quantum sensors for many-body physics. Image Credit: Natali _ Mis/Shutterstock.com
These sensors excelled in high-precision noise sensing, studying fluctuating currents and magnetic dynamics in materials like graphene and yttrium iron garnet. The study reviewed NV sensing platforms, linking their measurements to physical properties like correlation functions and order parameters inaccessible by other techniques. It concluded with insights into NV sensors' potential to reveal new aspects of condensed matter systems.
Related Work
Past work explored how NV centers advanced condensed matter sensing in diamonds by enabling nanoscale spatial resolution and momentum-resolved static and dynamic properties measurements. Unlike traditional techniques, NV centers provided insights into transverse current fluctuations, shear response, and spatially inhomogeneous momentum information, essential for understanding phenomena like Wigner crystallization and viscous hydrodynamics. Recent advances included novel NV sensing modalities, enhanced imaging methods, and efficient sampling techniques, offering new opportunities in condensed matter research.
Versatile High-Sensitivity NV Sensing
NV centers in diamond enable high-sensitivity sensing across diverse conditions, from cryogenic to nearly 1,000 K and gigapascal pressures. These centers operate through optical initialization, tailored interactions with external fields, and spin-dependent fluorescence detection. NV sensing modalities include optically detected magnetic resonance (ODMR) for direct current (DC) magnetic fields, Ramsey-based protocols for alternating current (AC) fields, and relaxometry for fluctuating fields.
NV platforms range from bulk diamond to nanoscale structures, each offering unique trade-offs in sensitivity, resolution, and ease of fabrication. Advances in diamond processing have enabled high-resolution scanning tips and nanostructures, allowing NV centers to probe static and dynamic properties at nanometer scales.
NV centers excel in detecting magnetic fields, electric fields, temperature, and strain, surpassing traditional techniques like scanning tunneling microscopy (STM) and magnetic force microscopy (MFM). Sensitivity improvements stem from increasing NV numbers, extending coherence times, and enhancing readout fidelity through advanced protocols like spin-to-charge conversion.
Achievable sensitivities span a wide range for DC and AC fields, with spatial resolution reaching nanoscale precision. NV centers have been positioned highly close to surfaces, enabling detailed studies of material properties. Emerging techniques, including machine learning for magnetization reconstruction and frequency mixing for broader spectral access, have further refined the capabilities of NV sensors, enabling unprecedented insights into nanoscale phenomena.
Quantitative NV Magnetometry Applications
NV magnetometry offers a powerful tool for quantitatively mapping stray magnetic fields. It facilitates precise measurements of the average areal magnetization in 2D materials, which can be used to validate model Hamiltonians and assess the quality and homogeneity of various compounds. This capability arises from the identical gyromagnetic ratio (γe) of NV centers, allowing for linear mapping of magnetic field variations to a frequency reference without additional calibration. NV magnetometry will enable researchers to infer physical properties from stray field maps through data analysis or reverse propagation, assuming magnetic anisotropies.
The method has proven particularly useful for determining magnetization strengths in 2D magnetic materials and thin-film magnets and in more complex systems like spin spirals in bulk multiferroics. The precision of these measurements, combined with temperature and field dependence analysis, is crucial in advancing the theoretical understanding of these materials. Additionally, NV magnetometry has been applied to validate theoretical predictions, such as surface magnetization in magnetoelectric antiferromagnets.
NV magnetometry played a key role in distinguishing between domain walls and characterizing magnetic skyrmions, providing insights into exchange interactions and winding numbers. It enabled the quantitative imaging of superconducting order, including measuring the London penetration depth (λL) in high-temperature superconductors. This technique also contributed to understanding magnonics and superconducting devices, offering new perspectives on their microstructures.
Additionally, the technique has been employed for current imaging, revealing spatial maps of current flow patterns that provide more detailed information than conventional transport measurements. It has opened avenues for exploring electron hydrodynamics in materials where electron-electron scattering dominates, offering direct spatial evidence of hydrodynamic behavior. By mapping current irregularities, NV magnetometry enables a deeper understanding of transport phenomena, including the role of electron-electron interactions in superconductivity, with applications that extend to graphene and other condensed matter systems.
NV Centers Noise Detection
The fluctuation-dissipation theorem connects material responses to thermal or quantum fluctuations, with NV centers offering a unique method for measuring local current and magnetic-field fluctuations in 2D systems. These centers can detect equilibrium and non-equilibrium states, providing insights into current noise, charge carriers, and wavevector-dependent noise. NV centers are useful in T1 and T2 spectroscopy to study transport properties, noise in graphene, and magnetic excitations. This technology allows for high-resolution nanoscale imaging and the exploration of noise in complex materials.
Conclusion
To sum up, NV magnetometry was applied to study weak, uncompensated moments in antiferromagnetic systems, enabling the exploration of magnetoelectrics and nanoscale domain imaging. It provided insights into time-reversal symmetry breaking, spatially inhomogeneous systems, and non-equilibrium dynamics in condensed matter physics. Additionally, NV centres were used to detect electric fields, temperature, and strain, offering valuable tools for studying deviations in heat and electronic transport.
Journal Reference
Rovny, J., et al. (2024). Nanoscale diamond quantum sensors for many-body physics. Nature Reviews Physics, 1-16. DOI: 10.1038/s42254-024-00775-4, https://www.nature.com/articles/s42254-024-00775-4
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