Probing the Evolution of the Electron Spin Wave Function of the Nitrogen-Vacancy Center in Diamond via Pressure Tuning
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2022-12-14 |
| Journal | Physical Review Applied |
| Authors | Kin On Ho, Man Yin Leung, Prithvi Reddy, Jianyu Xie, King Cho Wong |
| Institutions | Hong Kong University of Science and Technology, Chinese University of Hong Kong |
| Citations | 8 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled āExecutive SummaryāThis research introduces a novel, robust method for probing the electron spin wavefunction of solid-state qubits, specifically the Nitrogen Vacancy (NV-) center in diamond, by utilizing hydrostatic pressure tuning.
- Core Achievement: Demonstrated the first measurement of stress-dependent hyperfine interaction in a point defect system, using the nearest-neighbor 13C nuclear spin as an atomic-scale probe.
- Wavefunction Evolution: Applied pressure causes a prominent change in the NV electron spin wavefunction, resulting in an increase in electron spin density (Ī·).
- Orbital Rehybridization: Pressure induces orbital rehybridization, shifting the NV centerās bonds from sp3 towards a more sp2-like configuration.
- Method Validation: Experimental results derived from Optically Detected Magnetic Resonance (ODMR) show excellent qualitative agreement with independent ab initio calculations, validating the theoretical models without requiring fitting parameters.
- Technological Advantage: Pressure tuning provides a cleaner, stronger, and more isolated lattice perturbation effect compared to traditional thermal tuning, allowing for systematic studies of defect susceptibilities.
- Implication: This methodology can be universally adopted to investigate the wavefunctions of deep defects in other wide-bandgap semiconductors, crucial for advancing quantum sensing and computing applications.
Technical Specifications
Section titled āTechnical SpecificationsāThe following specifications detail the experimental parameters and the measured pressure susceptibility of the NV centerās 13C hyperfine structure.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Hydrostatic Pressure | 104.5 | kbar | Achieved using Diamond Anvil Cell (DAC) at room temperature. |
| Pressure Medium | 4:1 Methanol:Ethanol | N/A | Used to maintain hydrostatic conditions up to ~100 kbar. |
| Pressure Calibration Standard | dD/dP = 1.49 | MHz/kbar | Susceptibility of the NV center zero-field splitting (D) used for in situ pressure determination. |
| Ambient Hyperfine Splitting (Ahf(0)) | 127.69 Ā± 0.54 | MHz | Experimental average (AVG) for 13C ODMR. |
| Ahf Pressure Susceptibility (dAhf/dP) | 0.035 | MHz/kbar | Average experimental slope, indicating increasing electron spin density. |
| Ambient Center Frequency (Ī“hf(0)) | 2877.05 Ā± 0.38 | MHz | Experimental average (AVG) for 13C ODMR. |
| Ī“hf Pressure Susceptibility (dĪ“hf/dP) | 1.482 | MHz/kbar | Average experimental slope, dominated by the spin-spin dependence (dD/dP). |
| Calculated Hyperfine-Stress Interaction | Order of 0.1 | kHz/kbar | Component magnitude (dĪ“hf/dĻ), four orders < spin-spin dependence. |
| Orbital Hybridization Change | Decreases | N/A | p-orbital contribution ( |
| Electron Spin Density Change | Increases | N/A | Electron spin density (Ī·) increases under pressure (Fig 3f). |
Key Methodologies
Section titled āKey MethodologiesāThe experiment utilized a high-pressure Diamond Anvil Cell (DAC) setup combined with Optically Detected Magnetic Resonance (ODMR) spectroscopy to measure the NV center properties.
- Sample Preparation: 1-Āµm diamond nanoparticles (NDs) containing NV centers were drop-casted onto one of the diamond anvil culets.
- Pressure Apparatus: A Diamond Anvil Cell (DAC) was employed to generate high pressure, confining the sample and pressure medium within a metallic gasket.
- Microwave (MW) Delivery: A 150 Āµm-diameter omega-shaped gold micro-structure was fabricated directly on the anvil to serve as a reliable MW antenna for ODMR measurements.
- Hydrostatic Environment: A 4:1 methanol:ethanol mixture was used as the pressure-transmitting medium, ensuring excellent hydrostatic conditions up to approximately 100 kbar.
- Pressure Determination: Pressure was calibrated in situ by monitoring the center frequency (D) of the NV ODMR spectrum, leveraging the known pressure susceptibility (dD/dP = 1.49 MHz/kbar).
- Spectroscopic Measurement: ODMR was performed to track the 13C hyperfine structure. A non-uniform MW frequency step was implemented to maximize spectral resolution in the weak hyperfine resonance regions while minimizing total measurement time.
- Theoretical Comparison: Ab initio calculations were performed using the Vienna Ab initio Simulation Package (VASP) and the PBE functional to model the strain dependence of the NV centerās hyperfine levels, providing a direct, parameter-free comparison to experimental data.
Commercial Applications
Section titled āCommercial ApplicationsāThe ability to precisely characterize and control the NV center wavefunction under stress has direct implications for advanced quantum technologies and material science under extreme conditions.
- Quantum Sensing and Metrology:
- Development of highly sensitive, nanoscale quantum sensors capable of mapping local stress tensors and magnetic fields within materials and devices.
- Enabling precision measurements in extreme environments (e.g., high-pressure physics, cryogenic systems).
- Quantum Information Processing (QIP):
- Engineering robust quantum registers by accurately characterizing the susceptibility of nuclear spin qubits (like 13C) to external strain, leading to improved coherence protection.
- Optimizing NV center properties (spin density, hybridization) for enhanced spin initialization and readout fidelity.
- Deep Defect Engineering:
- Establishing a generalized methodology for investigating the wavefunctions of other deep defects in wide-bandgap semiconductors (e.g., SiC, GaN), which are critical for next-generation quantum hardware.
- High-Pressure Material Science:
- Providing a tool for microscopic investigation of phase transitions, magnetism, and electronic structure changes in correlated electron systems and superconductors under high pressure, complementing traditional bulk measurements.
- Semiconductor Device Reliability:
- Characterizing how mechanical stress, inherent in semiconductor fabrication and packaging, affects the performance and stability of solid-state quantum emitters and qubits.
View Original Abstract
Understanding the profile of a qubitās wave function is key to its quantum applications. Unlike conduct-ing systems, where a scanning tunneling microscope can be used to probe the electron distribution, there is no direct method for solid-state-defect-based qubits in wide-band-gap semiconductors. In this work, we use pressure as a tuning method and a nuclear spin as an atomic scale probe to monitor the hyperfine structure of negatively charged nitrogen-vacancy (N -V) centers in diamonds under pressure. We present a detailed study on the nearest-neighbor 13C hyperfine splitting in the optically detected magnetic reso-nance spectrum of N -V centers at different pressures. By examining the 13C hyperfine interaction upon pressurizing, we show that the N -V hyperfine parameters have prominent changes, resulting in an increase in the N -V electron spin density and rehybridization from sp3 to sp2 bonds. The ab initio calculations of strain dependence of the N -V centerās hyperfine levels are done independently. The theoretical results qualitatively agree well with experimental data without introducing any fitting parameters. Furthermore, this method can be adopted to probe the evolution of wave function in other defect systems. This potential capability could play a role in developing magnetometry and quantum information processing using the defect centers.