Abstract：
Quantum sensing with solid-state spin defects provides a powerful route to probe quantum materials with nanoscale resolution and sensitivity to both local fields and fluctuation dynamics. In this talk, I will present our work using NV centers in diamond and VB⁻ centers in hexagonal boron nitride as quantum sensors to investigate magnetic fluctuations and critical behavior in condensed-matter systems. I will also discuss recent progress in developing VB⁻ centers as ultra-proximal sensors compatible with 2D heterostructures. These efforts are motivated by rich correlated phenomena and moiré physics emerging in 2D moiré superlattices, where we have studied magneto-valley excitons via optical spectroscopy. Together, these research directions highlight quantum defect engineering as a promising approach for exploring emergent correlated states and for advancing hybrid light–spin quantum interfaces in 2D heterostructures.