Visualization of the Meissner Effect Using Miniaturized Quantum Magnetometers

At a Glance

Metadata	Details
Publication Date	2025-09-05
Journal	Applied Sciences
Authors	Wookyoung Choi, Chanhu Park, Jaebum Park, Dongkwon Lee, Myeongwon Lee
Institutions	Korea University, LG (South Korea)
Analysis	Full AI Review Included

Executive Summary

This research demonstrates a novel, non-destructive method for visualizing the Meissner effect using a miniaturized quantum magnetometer, offering significant advantages for diagnostics and education.

Core Achievement: Direct visualization and mapping of static magnetic field expulsion (Meissner effect) above a high-T_c Yttrium Barium Copper Oxide (YBCO) superconductor.
Technology: Utilizes a miniaturized scanning magnetometer based on ensemble Nitrogen-Vacancy (NV) centers in diamond, enabling millimeter-scale resolution vector magnetometry.
Operational Advantage: The NV quantum sensor operates entirely under ambient room-temperature conditions, drastically simplifying the setup compared to traditional cryogenic magnetic imaging techniques.
Data Acquisition: Vector magnetometry, leveraging four NV orientations, allows for the reconstruction of all three magnetic field components (B_x, B_y, B_z) and the total magnitude (B_norm).
Meissner Confirmation: Clear suppression and distortion of the magnetic field were observed when the YBCO was cooled below its critical temperature (T_c = 93 K), consistent with magnetic simulations.
Dual Functionality: The NV center simultaneously monitors temperature via the Zero-Field Splitting (ZFS) shift, qualitatively confirming that the YBCO sample is sufficiently cooled below T_c.
Application Suitability: The technique is highly practical for educational demonstrations of superconductivity and serves as an accessible, early-stage diagnostic tool for characterizing superconducting materials.

Technical Specifications

Parameter	Value	Unit	Context
Superconductor Material	YBCO (Yttrium Barium Copper Oxide)	N/A	High-T_c disk
Critical Temperature (T_c)	93	K	YBCO material property
YBCO Disk Dimensions	4.5 (Diameter) x 0.8 (Thickness)	cm	Sample geometry
NV Sensor Type	Ensemble NV centers in Type 1b diamond	N/A	Quantum sensor element
Diamond Dimensions	3 x 3 x 0.3	mm	Sensor crystal size
NV Density	~10¹³	cm^-3	Concentration in diamond
Sensor Operating Temp	Ambient Room Temperature	N/A	NV magnetometer operation
Excitation Laser Wavelength	532	nm	Green laser source
Excitation Laser Power	~24	mW	Power delivered to diamond
Microwave Frequency	~3	GHz	Used for Electron Spin Resonance (ESR)
Scanning Area	4.3 x 4.3	cm²	Total mapped area
Scanning Step Size	2.15	mm	Spatial resolution of mapping
Sensor-Sample Separation (h)	1.7 (min) to 2.1 (max)	cm	Vertical distance during measurement
Measurement Time per Step	20	s	Includes 18 s acquisition + 2 s settling
ZFS Temperature Sensitivity (dD/dT)	-74.2	kHz/K	Used for temperature monitoring (valid 280-330 K range)

Key Methodologies

The visualization of the Meissner effect was achieved through a custom-built scanning quantum magnetometer integrating NV centers and a cryogenically cooled sample stage.

Experimental Setup: A miniaturized scanning magnetometer, featuring a fiber-coupled NV-based quantum sensor, was mounted on a 2D scanning stage above a 3D-printed plastic housing.
Sample Preparation: A YBCO disk was placed in the housing, supported by four Neodymium (Nd) magnets used to generate the external magnetic field necessary for levitation and stabilization.
Cryogenic Cooling: Liquid nitrogen was continuously supplied to the housing to cool the YBCO below its critical temperature (T < T_c) for superconducting state measurements. The NV sensor itself remained at ambient room temperature.
Optical and Microwave Control:
- NV centers were initialized and read out optically using a 532 nm laser.
- Electron Spin Resonance (ESR) was driven by a ~3 GHz microwave field delivered via an integrated double split-ring resonator.
Vector Magnetometry (ODMR):
- The Optically Detected Magnetic Resonance (ODMR) spectrum was measured using lock-in detection, revealing four pairs of Zeeman-split resonances corresponding to the four possible NV orientations in the diamond lattice.
- Frequency shifts of these four groups were analyzed to reconstruct the three-dimensional magnetic field components (B_x, B_y, B_z) at each point.
Scanning and Mapping: The sensor was translated across a 4.3 cm x 4.3 cm area with a 2.15 mm step size. Measurements were taken both above T_c (normal state) and below T_c (superconducting state) at various heights (h = 1.7 cm, 1.9 cm, 2.1 cm).
Temperature Monitoring: The common frequency shift (f_c) of the NV spin states was tracked simultaneously with magnetic field measurements. This shift, related to the temperature-dependent Zero-Field Splitting D(T), provided qualitative confirmation that the YBCO was cooled below T_c via thermal radiation detection.
Simulation Validation: Experimental results were compared against magnetic simulations performed using COMSOL Multiphysics 5.4, assuming perfect diamagnetism for the YBCO below T_c.

Commercial Applications

The demonstrated technology is highly relevant across several engineering and scientific sectors due to its compact, room-temperature sensor operation and high sensitivity.

Quantum Sensing and Metrology: Provides a platform for developing compact, robust, and high-sensitivity quantum magnetometers suitable for operation outside of specialized cryogenic laboratories.
Superconductivity Diagnostics: Enables non-destructive, rapid characterization and quality control of new superconducting materials (e.g., tapes, wires, thin films) by mapping flux expulsion and trapping.
Educational Technology: Offers an accessible and intuitive method for demonstrating fundamental physics principles, such as the Meissner effect, in university and research teaching labs.
Magnetic Levitation (Maglev) Systems: Applicable for characterizing and optimizing the magnetic field profiles generated by permanent magnet arrays interacting with superconductors in levitation and stabilization systems.
Non-Invasive Material Testing: The technique can be extended to probe other material properties where local magnetic fields are relevant, provided the field profiles are resolvable by the sensor.

View Original Abstract

The direct visualization of the Meissner effect is achieved by mapping the expulsion of static magnetic fields from a high-TC superconductor, specifically Yttrium Barium Copper Oxide (YBCO). This is accomplished using a miniaturized scanning magnetometer based on an ensemble of nitrogen-vacancy (NV) centers in diamond, operating under ambient room-temperature conditions. By comparing the magnetic field profiles above the YBCO sample at temperatures above and below its critical temperature TC, we observe clear suppression and distortion of the magnetic field in the superconducting state. These observations are consistent with both magnetic simulations and expected characteristics of the Meissner effect. This work introduces a novel and practical method for visualizing the Meissner effect, offering potential applications in educational demonstrations and the diagnostic testing of superconductivity using room-temperature quantum magnetometry.

Tech Support

Original Source

DOI: https://doi.org/10.3390/app15179766

References

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