Electron-phonon processes of the nitrogen-vacancy center in diamond

At a Glance

Metadata	Details
Publication Date	2015-08-21
Journal	Physical Review B
Authors	Taras Plakhotnik, Marcus W. Doherty, Neil B. Manson
Institutions	The University of Queensland, Australian National University
Citations	36
Analysis	Full AI Review Included

Technical Documentation and Analysis: Electron-Phonon Processes in NV Diamond

Executive Summary

This document analyzes the research on high-temperature electron-phonon dynamics in Nitrogen-Vacancy (NV^-) centers, relevant for advanced quantum sensing and computing applications.

Core Achievement: Systematic study of NV center Optically Detected Magnetic Resonance (ODMR) spanning 295 K to 550 K, establishing the motional narrowing model applicability at elevated temperatures.
Fundamental Insight: The research resolves previous inconsistencies in Zero-Phonon Line (ZPL) broadening models by confirming that quadratic interactions with symmetric A₁ phonon modes are essential above 30 K, critical for high-temperature device engineering.
Material Relevance: Results obtained in nanodiamond are confirmed to capture intrinsic phenomena consistent with bulk diamond, validating the use of high-quality Single Crystal Diamond (SCD) substrates for practical device fabrication.
Extracted Parameters: Precise phenomenological phonon cutoff energies (Ω_E ≈ 13 meV, Ω_A ≈ 37 meV) and temperature-dependent population transfer rates are determined, providing essential inputs for future quantum device simulation.
6CCVD Value Proposition: 6CCVD provides the necessary high-purity Single Crystal Diamond (SCD) material, custom dimensioning, and integrated metalization required to transition these fundamental research findings into scalable, robust quantum devices operating under ambient and elevated conditions.

Technical Specifications

Parameter	Value	Unit	Context
Operational Temperature Range	295 - 550	K	ODMR measurement range (Ambient to Elevated)
Excitation Wavelength	532	nm	Continuous Wave (CW) Laser Source
Zero Phonon Line (ZPL) Energy	1.946	eV	Visible optical transition
³E Strain Splitting (hξ₁)	4.6 ± 0.2	meV	Measured value in nanodiamond
Fitted Room Temperature Linewidth (Γ_ODMR)	55	MHz	Homogenous component
E-Phonon Cutoff Energy (Ω_E)	13 ± 1	meV	Jahn-Teller interaction parameter
A₁-Phonon Cutoff Energy (Ω_A)	37 ± 2	meV	Quadratic interaction parameter
RF Power Levels Used	50, 200, 400	mW	Used for Rabi frequency drive
ODMR Frequency Range (Example)	400 - 430	MHz	Observed frequency range at 315 K
Approximate Relaxation Rate (γ₁)	≈ 22	MHz	Effective spin relaxation rate

Key Methodologies

The experiment successfully characterized the electron-phonon coupling using CW-ODMR under highly controlled thermal and RF conditions.

Sample Preparation: Nanodiamonds (average diameter ~30 nm, containing ~15 NV centers) were spin coated onto a silica substrate.
Optical Setup: An epifluorescence design was used for 532 nm CW laser excitation and subsequent fluorescence collection.
RF Delivery: An RF magnetic field, used to drive the NV spin resonances, was generated by a gold wire deposited directly onto the substrate near the nanodiamonds.
In-Situ Temperature Control: Local heating was achieved by carefully overlapping the excitation laser spot with the RF gold wire. The optical heating provided control over the sample temperature in the 295 K - 550 K range.
Spectroscopy: Continuous Wave Optically Detected Magnetic Resonance (CW-ODMR) spectra were recorded, analyzing the temperature-dependent linewidth, contrast, and splitting of the ³E excited state.
Modeling and Fitting: Data were systematically fitted using a five-parameter motional narrowing model in the fast exchange approximation, incorporating both linear E-phonon (Jahn-Teller) and quadratic A₁-phonon interactions to model the ZPL broadening.

6CCVD Solutions & Capabilities

This research confirms the potential for NV-diamond quantum devices to operate effectively across a wide temperature spectrum, provided the material quality (low strain, controlled defect density) is maintained. 6CCVD is uniquely positioned to supply the required high-specification diamond material and integrated device components.

Applicable Materials

To replicate and extend this high-temperature research into scalable devices, researchers require robust, low-strain material capable of supporting optimal NV spin properties.

Research Requirement	6CCVD Applicable Material	Justification / Benefit
High-Purity NV Host	Single Crystal Diamond (SCD)	SCD offers superior crystalline quality, extremely low strain, and minimal nitrogen/other impurities, maximizing ground state spin coherence (T₂) essential for sensing.
High-Density Sensor Arrays	Optical Grade PCD Plates	For applications requiring large-area coverage or sensor arrays, 6CCVD PCD offers wafers up to 125mm, providing robust, high-surface-area substrates.
Cryogenic & Ambient Systems	SCD (0.1µm - 500µm)	Precise thickness control is crucial for managing strain and optimizing light collection efficiency (ZPL quality) across all operating temperatures.

Customization Potential for Advanced NV Platforms

The research used a gold wire deposited on silica for RF drive and thermal control. 6CCVD offers the capability to integrate these functionalities directly onto the diamond substrate, streamlining fabrication and improving device robustness.

Integrated Metalization: 6CCVD provides in-house sputtering and lithography for depositing high-conductivity, high-temperature stable metals, including Au, Pt, Ti, and Cu. This allows researchers to integrate RF antennas, micro-heaters (for controlled thermal operation up to 550 K as demonstrated in the paper), and signal leads directly onto the SCD or PCD surface.
Precision Polishing & Surface Quality: High-resolution optical spectroscopy (ZPL measurement) is sensitive to surface roughness. 6CCVD guarantees ultra-low surface roughness: Ra < 1nm for SCD and Ra < 5nm for inch-size PCD plates, ensuring minimal optical scatter and maximized light coupling efficiency.
Custom Dimensions: While the paper used nanodiamonds, scalable quantum devices require wafer-scale processing. 6CCVD delivers custom PCD plates up to 125mm in diameter and SCD substrates up to 10mm in thickness, enabling industrial-scale fabrication of high-temperature quantum sensors.

Engineering Support

The findings regarding the crucial role of A₁ phonon modes require careful material selection and design to mitigate unwanted dephasing at ambient temperatures.

6CCVD’s in-house PhD engineering team specializes in diamond material optimization for NV applications. We offer comprehensive support for projects involving similar High-Temperature Quantum Sensing and Spin-Phonon Coupling research, assisting customers in selecting the ideal material grade, crystal orientation, and defect engineering strategy to achieve targeted operational stability and coherence times.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Applications of the negatively charged nitrogen-vacancy center in diamond exploit the center’s unique optical and spin properties, which at ambient temperature are predominately governed by electron-phonon interactions. Here, we investigate these interactions at ambient and elevated temperatures by observing the motional narrowing of the center’s excited-state spin resonances. We determine that the center’s Jahn-Teller dynamics are much slower than currently believed and that they do not solely account for the broadening of the center’s optical resonance above cryogenic temperatures. We show that the inclusion of interactions with symmetric phonon modes can explain the observed broadening and resolve the current inconsistencies in the literature. However, our model also reveals unexpected features of the electron-phonon processes that coincide with other poorly understood vibronic features of the center and require further investigation.

Tech Support

Original Source

DOI: https://doi.org/10.1103/physrevb.92.081203