[Paper Review] Imaging the local charge environment of nitrogen-vacancy centers in diamond

Thomas Mittiga, Satcher Hsieh+9 more|Sep 5, 2018

Diamond and Carbon-based Materials Research4 citations

TL;DR

This paper demonstrates that local electric fields, not lattice strain, dominate the zero-field magnetic resonance spectra of nitrogen-vacancy (NV) centers in diamond. By developing a microscopic charge model and using microwave-driven dark-state spectroscopy, the authors achieve nanoscale localization of individual charges (within ~5 nm) via polarization-dependent amplitude imbalance in ODMR signals, enabling precise vector electric field reconstruction at single-defect resolution.

ABSTRACT

Characterizing the local internal environment surrounding solid-state spin defects is crucial to harnessing them as nanoscale sensors of external fields. This is especially germane to the case of defect ensembles which can exhibit a complex interplay between interactions, internal fields and lattice strain. Working with the nitrogen-vacancy (NV) center in diamond, we demonstrate that local electric fields dominate the magnetic resonance behavior of NV ensembles at low magnetic field. We introduce a simple microscopic model that quantitatively captures the observed spectra for samples with NV concentrations spanning over two orders of magnitude. Motivated by this understanding, we propose and implement a novel method for the nanoscale localization of individual charges within the diamond lattice; our approach relies upon the fact that the charge induces an NV dark state which depends on the electric field orientation.

Motivation & Objective

• To identify the dominant source of spectral broadening and splitting in zero-field NV ensemble magnetic resonance spectra.
• To understand the role of local charge environments in modifying NV spin resonance behavior, particularly in high-density NV systems.
• To develop a method for nanoscale imaging of individual charges near NV centers using their electric field effects on NV spin states.
• To enable precise reconstruction of the vector electric field at the NV center by measuring polarization-dependent microwave transition amplitudes.
• To provide a framework for improving NV-based quantum sensing in low-field and zero-field regimes by accounting for local charge effects.

Proposed method

• Developed a microscopic charge model that accounts for random local electric fields from nearby charges, explaining observed ODMR spectra across NV concentrations spanning two orders of magnitude.
• Utilized optically detected magnetic resonance (ODMR) to measure transition amplitudes between the |m_s = 0⟩ state and the electric-field-split |±⟩ states of single NV centers.
• Applied linearly polarized microwave fields with tunable polarization angle φ_MW to probe the electric field orientation φ_E via the imbalance in transition amplitudes A_+ and A_-.
• Defined the imbalance I = (A_+ - A_-)/(A_+ + A_-), which follows the relation I ∝ -cos(2φ_MW + φ_E), enabling extraction of φ_E from experimental data.
• Combined measured splitting (Π_z = 30(50) kHz, Π_⊥ = 650(10) kHz) and phase offset (φ_E = 124(5)°) to reconstruct the full vector electric field at the NV center.
• Performed long-term monitoring to confirm field stability, indicating a stationary charge source, and localized the charge to within ~5 nm using confidence maps.

Experimental results

Research questions

• RQ1 What is the dominant source of spectral splitting in zero-field ODMR spectra of NV ensembles—lattice strain or local electric fields?
• RQ2 How do local charges near NV centers affect the magnetic resonance transition amplitudes and their polarization dependence?
• RQ3 Can the vector electric field at a single NV center be reconstructed from ODMR measurements using microwave polarization tuning?
• RQ4 What is the spatial resolution and confidence in localizing individual charges using this method?
• RQ5 How does the presence of local electric fields influence the resilience of NV centers to magnetic noise and their utility in quantum sensing?

Key findings

• Local electric fields, not lattice strain, are the primary source of spectral splitting in zero-field ODMR spectra of NV ensembles in diamond.
• The observed ODMR spectra for NV concentrations spanning two orders of magnitude are quantitatively captured by a microscopic charge model incorporating random local electric fields.
• The amplitude imbalance in the |m_s = 0⟩ ↔ |±⟩ transitions of a single NV center depends on the relative angle between the microwave polarization and the electric field orientation, with I ∝ -cos(2φ_MW + φ_E).
• The electric field orientation φ_E was extracted as 124(5)°, and the field magnitude was reconstructed as Π_z = 30(50) kHz and Π_⊥ = 650(10) kHz, consistent with a single stationary charge.
• The charge was localized to within ~5 nm of the NV center with high confidence, and the field showed no measurable drift over months, indicating a stable, localized source.
• The method enables nanoscale imaging of individual charges in diamond with vector electric field resolution, opening new pathways for quantum sensing and defect engineering.