UC San Diego

Optically active spin defects with excellent quantum coherence, single-spin addressability, ultra high field sensitivity, and remarkable functionalities are integral to emergent modern quantum technologies, material sciences, and a broad range of forefront fundamental scientific research. In this thesis, we mainly utilize spin defects to probe and measure the properties of condensed matter system at the nanoscale level. Through non-invasive method, we optically access the intrinsic spin transport properties of an archetypical AFI α-Fe2O3 via nitrogen vacancy quantum spin sensors. By NV relaxometry measurements, the frequency dependent dynamic fluctuations of the spin density of α-Fe2O3 along the Néel order parameter are successfully detected, from which an intrinsic spin diffusion constant of α-Fe2O3 is experimentally measured in the absence of external spin biases. Furthermore, we report nanoscale quantum imaging of low-dimensional ferromagnetism sustained in a van der Waals ferromagnet Fe3GeTe2 by another two-dimensional quantum sensor, boron vacancy in hexagonal boron nitride (hBN), which demonstrates the capability of spin defects in hBN to investigate local magnetic properties of layered materials in an accessible and precise way. This capability can be readily extended to a broad range of miniaturized van der Waals heterostructure systems. Our study shows that spin defects can probe both static and dynamic nanoscale magnetic textures in condensed matter systems.