Critical fluctuation and noise spectra in two-dimensional Fe$_{3}$GeTe$_{2}$ magnets

• Main Authors: Li, Yuxin, Ding, Zhe, Wang, Chen, Sun, Haoyu, Chen, Zhousheng, Wang, Pengfei, Wang, Ya, Gong, Ming, Zeng, Hualing, Shi, Fazhan, Du, Jiangfeng
• Format: Journal Article
• Language: English
• Published: 30.06.2024
• Subjects: Physics - Mesoscale and Nanoscale Physics; Physics - Quantum Physics
• DOI: 10.48550/arxiv.2407.00647

Critical fluctuations play a fundamental role in determining the spin orders for low-dimensional quantum materials, especially for recently discovered two-dimensional (2D) magnets. Here we employ the quantum decoherence imaging technique utilizing nitrogen-vacancy centers in diamond to explore the critical magnetic fluctuations and the associated temporal spin noise in van der Waals magnet $\rm{Fe_{3}GeTe_{2}}$. We show that the critical fluctuation contributes to a random magnetic field characterized by the noise spectra, which can be changed dramatically near the critical temperature $T_c$. A theoretical model to describe this phenomenon is developed, showing that the spectral density is characterized by a $1/f$ noise near the $T_c$, while away from this point it behaves like a white noise. The crossover at a certain temperature between these two situations is determined by changing of the distance between the sample and the diamond. This work provides a new way to study critical fluctuation and to extract some of the critical exponents, which may greatly deepen our understanding of criticality in a wide range of physical systems.