EB-04 Quantum Noise Spectroscopy of Critical Dynamics in Two-dimensional Magnets
Creators: Shubhayu Chatterjee
Francisco Machado
Mark Ziffer
Eugene Demler
Norman Yao
Carlos Meriles
Jim Schuck
Jonathan Owen and Abhay Pasupathy
Publisher: name: IEEE
Year: 2025

Imaging spatial and temporal correlations of spins in two-dimensional (2d) magnets presents a significant challenge, since traditional scattering and spectroscopic tools do not apply. In this talk, I will propose and analyze a new technique based on quantum states of 'color defects' in solid state materials, such as nitrogen-vacancy (NV) sensors in diamond, to probe spin-correlations with energy and momentum resolution in 2d magnets. Specifically, I will argue that the decoherence of the defect 'probe qubit' due to magnetic noise, caused by spin fluctuations in a proximate 2d magnetic flake, can provide valuable information about phase transitions in 2d magnets. I will show that such decoherence-based noise spectroscopy directly targets slow critical dynamics in 2d magnets, and can hence be used to diagnose the universality class associated with the magnetic transition and extract critical exponents via a scaling analysis. Finally, to illustrate the ability of magnetic noise spectroscopy to identify the nature of critical fluctuations in magnets, I will discuss its recent application to trilayer CrSBr, a truly two-dimensional magnet that undergoes a magnetic phase transition around 140 K.References: F. Machado, E. A. Demler, N. Y. Yao and S. Chatterjee, Phys. Rev. Lett., 131, 070801 (2023) M. E. Ziffer, F. Machado, B. Ursprung, A. Lozovoi, A. B. Tazi, Z. Yuan, M. E. Ziebel, T. Delord, N. Zeng, E. Telford, D. G. Chica, D. W. deQuilettes, X. Zhu, J. C Hone, K. L Shepard, X. Roy, N. P. de Leon, E. J. Davis, S. Chatterjee, C. A. Meriles, J. S. Owen, P. J. Schuck and A. N. Pasupathy, arXiv:2407.05614 (2024)
Imaging spatial and temporal correlations of spins in two-dimensional (2d) magnets presents a significant challenge, since traditional scattering and spectroscopic tools do not apply. In this talk, I will propose and analyze a new technique based on quantum states of 'color defects' in solid state materials, such as nitrogen-vacancy (NV) sensors in diamond, to probe spin-correlations with energy and momentum resolution in 2d magnets. Specifically, I will argue that the decoherence of the defect 'probe qubit' due to magnetic noise, caused by spin fluctuations in a proximate 2d magnetic flake, can provide valuable information about phase transitions in 2d magnets. I will show that such decoherence-based noise spectroscopy directly targets slow critical dynamics in 2d magnets, and can hence be used to diagnose the universality class associated with the magnetic transition and extract critical exponents via a scaling analysis. Finally, to illustrate the ability of magnetic noise spectroscopy to identify the nature of critical fluctuations in magnets, I will discuss its recent application to trilayer CrSBr, a truly two-dimensional magnet that undergoes a magnetic phase transition around 140 K.References: F. Machado, E. A. Demler, N. Y. Yao and S. Chatterjee, Phys. Rev. Lett., 131, 070801 (2023) M. E. Ziffer, F. Machado, B. Ursprung, A. Lozovoi, A. B. Tazi, Z. Yuan, M. E. Ziebel, T. Delord, N. Zeng, E. Telford, D. G. Chica, D. W. deQuilettes, X. Zhu, J. C Hone, K. L Shepard, X. Roy, N. P. de Leon, E. J. Davis, S. Chatterjee, C. A. Meriles, J. S. Owen, P. J. Schuck and A. N. Pasupathy, arXiv:2407.05614 (2024)