# Nanotube spin defects for omnidirectional magnetic field sensing

**Authors:** Xingyu Gao, Sumukh Vaidya, Saakshi Dikshit, Peng Ju, Kunhong Shen, Yuanbin Jin, Shixiong Zhang, Tongcang Li  
**arXiv:** [2310.02709](https://arxiv.org/abs/2310.02709)  
**Date:** 2023-10-04  
**Summary page:** https://www.summarizepaper.com/en/paper/2310.02709v1/

## Key points

- Optically addressable spin defects in one-dimensional (1D) van der Waals (vdW) nanotubes, specifically boron nitride nanotubes (BNNTs), have been successfully observed at room temperature.
- These BNNT spin defects exhibit a ground state with a spin value of $S=1/2 and lack an intrinsic quantization axis, enabling orientation-independent magnetic field sensing capabilities.
- Researchers demonstrated anisotropic magnetization behavior in a 2D magnet by leveraging the orientation-independent nature of BNNT spin defects, challenging conventional spin $S=1$ defects like diamond nitrogen-vacancy centers.
- A method was developed to deterministically transfer a BNNT onto a cantilever for scanning probe magnetometry with unprecedented precision.
- This advancement opens up possibilities for atomic-scale quantum sensing of magnetic fields in any direction, offering new avenues for high-resolution imaging and manipulation at the nanoscale.

## Summary

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In the realm of nanoscale quantum sensing, optically addressable spin defects have played a crucial role in advancing the field. These defects, found in both three-dimensional (3D) crystals and two-dimensional (2D) van der Waals (vdW) materials, have been extensively studied. However, one-dimensional (1D) vdW nanotubes have not been fully explored until now. These tiny tubes offer unique advantages due to their small size in two dimensions and the absence of dangling bonds on their side walls. Recently, a team of researchers led by Xingyu Gao, Sumukh Vaidya, Saakshi Dikshit, Peng Ju, Kunhong Shen, Yuanbin Jin, Shixiong Zhang, and Tongcang Li made a breakthrough discovery in this area. They successfully observed single optically addressable spin defects in boron nitride nanotubes (BNNTs) at room temperature. Their findings revealed that these BNNT spin defects exhibit a ground state with a spin value of $S=1/2$ and lack an intrinsic quantization axis. This unique characteristic enables orientation-independent magnetic field sensing capabilities. The significance of this discovery is further underscored by its practical applications. By leveraging the orientation-independent nature of these BNNT spin defects, the researchers were able to observe anisotropic magnetization behavior in a 2D magnet when subjected to magnetic fields along orthogonal directions. This achievement poses a challenge for conventional spin $S=1$ defects like diamond nitrogen-vacancy centers. Moreover, the team developed a method to deterministically transfer a BNNT onto a cantilever, enabling them to demonstrate scanning probe magnetometry with unprecedented precision. This advancement paves the way for atomic-scale quantum sensing of magnetic fields in any direction, offering new possibilities for high-resolution imaging and manipulation at the nanoscale. In conclusion, this study represents a significant step forward in harnessing the potential of nanotube spin defects for omnidirectional magnetic field sensing and opens up exciting avenues for further exploration and innovation in the field of quantum sensing technologies.