Spin Dynamics of Two-Dimensional V_B^- Ensembles in Hexagonal Boron Nitride

Strongly interacting color-center ensembles are conventionally realized in three-dimensional systems. While these systems have been widely used as quantum sensors and as simulator platforms for studying many-body dynamics, accessing lower-dimensional physics with solid-state color centers remains an open challenge. Here, we investigate the many-body dynamics of ensembles of negatively charged boron vacancy (V_B^-) defects in few-layer hexagonal boron nitride (hBN) flakes, where the flake thickness is smaller than the average inter-defect spacing. In this regime, we show that the emergent dynamics are governed by native dipolar interactions between the V_B^- defects. In particular, we employ a form of many-body noise spectroscopy in which the system dimensionality directly manifests in the temporal profile of V_B^- decoherence dynamics. Building on this, we measure local spin–spin autocorrelation functions to probe and compare spin transport in two-dimensional thin flakes and three-dimensional bulk ensembles.