Light dark matter search with nitrogen-vacancy centers in diamonds

At a Glance

Metadata	Details
Publication Date	2025-03-12
Journal	Journal of High Energy Physics
Authors	So Chigusa, M. Hazumi, Ernst David Herbschleb, Norikazu Mizuochi, Kazunori Nakayama
Institutions	The University of Tokyo, Kavli Institute for the Physics and Mathematics of the Universe
Citations	4
Analysis	Full AI Review Included

Technical Documentation & Analysis: Light Dark Matter Search using NV Centers in Diamond

Executive Summary

This research proposes a highly sensitive method for detecting light bosonic dark matter (axions and dark photons) by exploiting the precise magnetic sensing capabilities of Nitrogen-Vacancy (NV) centers in diamond. 6CCVD is positioned as the essential material supplier to realize the ambitious experimental parameters required for this breakthrough research.

Core Application: Direct search for light dark matter (axion-like particles, dark photons) via their coupling to the electron spin, manifesting as an effective oscillating magnetic field (B_eff).
Methodology: Utilizes high-sensitivity NV center ensemble magnetometry, employing both DC (Ramsey sequence) and AC (Hahn-echo sequence) protocols to maximize coherence time (T₂) and filter environmental noise.
Sensitivity Projection: Theoretical projections show the potential to surpass current experimental and observational limits on dark matter couplings (g_aee and ε).
Material Requirement: Achieving the highest sensitivity (N = 10²⁰ NV centers) necessitates synthesizing ultra-large volumes (10³ cm³) of high-purity, low-strain diamond with controlled NV concentration (1.6 x 10¹⁷ cm^-3).
6CCVD Value Proposition: We provide the necessary large-area Polycrystalline Diamond (PCD) wafers (up to 125mm) and thick Single Crystal Diamond (SCD) substrates (up to 10mm) required for scaling NV ensemble experiments to the required volume and coherence performance.
Critical Material Parameter: Sensitivity is fundamentally limited by the spin coherence time (T₂/T₂*), demanding MPCVD diamond with exceptional crystalline quality and minimal defects.

Technical Specifications

The following parameters are critical for replicating and extending the NV-diamond dark matter search experiments:

Parameter	Value	Unit	Context
NV Center State	NV^-	N/A	Negatively charged spin triplet state
Zero-Field Splitting (D)	2.87	GHz	Ground state energy separation
Energy Gap (2πD)	11.9	µeV	Equivalent energy difference
DC Magnetometry Time (T₂*)	~1	µs	Typical spin dephasing time for ensembles
AC Magnetometry Time (T₂)	~50	µs	State-of-the-art transversal coherence time
Longest T₂ Reported	0.6	s	Achieved at 77 K (low temperature)
Target NV Count (N)	10¹² to 10²⁰	NVs	Required for high-sensitivity setups
Required Volume (for N=10²⁰)	10³	cm³	Based on 1.6 x 10¹⁷ cm^-3 concentration
Typical Precession Time (τ)	0.5	µs	Used for sensitivity calculations in figures
Dark Matter Velocity (v_DM)	10^-3	c	Typical velocity around Earth
Dark Matter Density (ρ_DM)	0.4	GeV/cm³	Local dark matter energy density

Key Methodologies

The proposed dark matter search relies on precise control over the NV spin state using microwave and magnetic fields, requiring ultra-stable diamond material properties.

NV Center Synthesis and Alignment: High-density NV ensembles (up to 1.6 x 10¹⁷ cm^-3) must be created, typically via nitrogen doping during MPCVD growth or subsequent implantation. For optimal sensitivity, the orientation of the NV centers must be aligned (e.g., along the [111] axis).
DC Magnetometry (Ramsey Sequence):
- Initialization: Optical pumping prepares the NV spin state to |0>.
- Pulse 1: A π/2 microwave pulse, tuned to the transition frequency ω⁺ (2πD + γ_eB₀), creates a superposition of |0> and |+>.
- Free Precession: The spin precesses for duration τ (limited by T₂*).
- Pulse 2 & Readout: A second π/2 pulse converts the accumulated phase (φ) into a measurable population difference, read out via fluorescence.
AC Magnetometry (Hahn-Echo Sequence):
- Used for detecting oscillating dark matter signals (mτ ≥ 2π) and extending coherence time (T₂ >> T₂*).
- An additional π pulse is applied at the central time τ/2 to cancel static magnetic noise and DC-like impurities, allowing for longer measurement times.
Resonance Search: By tuning the bias magnetic field (B₀), the energy gap ω⁺ can be matched to the dark matter mass (m), providing a resonant enhancement factor of up to 2 x 10⁴ (for τ/1 µs).

6CCVD Solutions & Capabilities

6CCVD’s expertise in large-area, high-purity MPCVD diamond is directly applicable to overcoming the scaling challenges identified in this research, particularly the need for massive NV ensembles and extended coherence times.

Applicable Materials

To achieve the required NV density and volume while maintaining high quantum performance, 6CCVD recommends the following materials:

Optical Grade Single Crystal Diamond (SCD):
- Purpose: Essential for achieving the longest possible coherence times (T₂ up to 0.6 s) due to its ultra-low strain and high crystalline purity. This material is critical for the low-mass, high-sensitivity AC magnetometry regimes.
- Specifications: SCD wafers with Ra < 1nm polishing, suitable for subsequent high-fidelity NV creation (implantation or controlled doping).
Large-Area Polycrystalline Diamond (PCD) Substrates:
- Purpose: Necessary for scaling the ensemble volume to the target 10³ cm³ (N = 10²⁰). The paper notes the need for combining many sensors; large PCD wafers minimize the number of required units.
- Specifications: PCD plates up to 125mm in diameter, with custom thicknesses up to 10mm for bulk volume experiments. Polishing to Ra < 5nm is available for optical access.
Controlled Nitrogen Doping:
- Purpose: Precise control over the nitrogen concentration (N) is required to achieve the target 1.6 x 10¹⁷ cm^-3 density while managing the trade-off between NV count and T₂* degradation.
- Capability: 6CCVD offers custom nitrogen doping during MPCVD growth to meet specific concentration targets for NV precursor creation.

Customization Potential

The experimental requirements demand specialized material preparation and geometry, which 6CCVD is uniquely equipped to handle:

Requirement from Paper	6CCVD Customization Capability	Benefit to Researcher
Large Volume (10³ cm³)	Plates/wafers up to 125mm (PCD) and Substrates up to 10mm thick.	Reduces the number of individual sensors needed for N=10²⁰ ensemble size.
Thin Wafers (e.g., 70 µm)	Custom SCD/PCD thickness from 0.1µm to 500µm.	Allows optimization for specific laser power requirements and microwave homogeneity.
NV Alignment	Provision of specific crystal orientations (e.g., (111) or (100) SCD).	Enables post-growth techniques for perfect preferential orientation of NV centers, maximizing signal coherence.
Microwave/RF Integration	Custom Metalization services (Au, Pt, Pd, Ti, W, Cu).	Facilitates integration of microwave antennas and electrodes directly onto the diamond surface for pulse delivery.

Engineering Support

6CCVD’s in-house PhD team specializes in the material science of quantum defects and can provide crucial support for projects focused on NV-Center Quantum Sensing and Dark Matter Detection.

We offer consultation on:

Optimizing nitrogen concentration and post-processing (e.g., annealing) to maximize the yield of NV^- centers.
Selecting the optimal diamond grade (SCD vs. PCD) based on the required coherence time (T₂) versus the required ensemble volume (N).
Designing custom geometries and metalization layers for efficient microwave delivery and magnetic field biasing (B₀).

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly. We offer global shipping (DDU default, DDP available) to ensure timely delivery of mission-critical materials worldwide.

View Original Abstract

A bstract We propose an approach to directly search for light dark matter, such as the axion or the dark photon, by using magnetometry with nitrogen-vacancy centers in diamonds. If the dark matter couples to the electron spin, it affects the evolution of the Bloch vectors consisting of the spin triplet states, which may be detected through several magnetometry techniques. We give several concrete examples with the use of dc and ac magnetometry and estimate the sensitivity on dark matter couplings.

Tech Support

Original Source

DOI: https://doi.org/10.1007/jhep03(2025)083