Fig. 1: Experiment setup and pulse sequences.
From: Critical fluctuations and noise spectra in two-dimensional Fe3GeTe2 magnets
a Exfoliated FGT flakes are transferred to a [100] oriented diamond chip with single-layer ensemble NV centers. Black arrows in the diamond chip indicate the four possible orientations of the NV centers. Microwaves are radiated through an Ω-shaped wave guide, and the magnetic field B0 is applied in-plane. hBN substrate layers are placed above and below the FGT flakes. Inset: Crystal structure of FGT and NV centers, where d denotes the NV-FGT distance. The crystal data were obtained at SpringerMaterials59. b Hahn-echo pulse sequences for wide-field coherence detection. Laser pulse initializes the state of NV centers to \(\left\vert 0\right\rangle\) and reads out the final state. The first π/2 microwave pulse drives the system to a superposition state. After free evolution for time τ, a π-pulse decouples noise components with frequencies beyond the 1/2τ band. Final π/2 or 3π/2 pulses convert coherence to \(\left\vert 0\right\rangle\) or \(\left\vert 1\right\rangle\) populations. A CMOS camera records photoluminescence from these populations as signal and reference frames, respectively. Each subsequence executes N times per frame. The pulse sequence is averaged over M ~100–200 times for each τ.
