Development of Femtosecond Noise Correlation Spectroscopy Enabled by Digitizer-Based Statistical Operation
Poster-In-person
Abstract
In magnetic materials, magnetization fluctuates continuously due to thermal fluctuations, even in equilibrium. Near the phase transition temperature, these fluctuations intensify and play a key role in driving the transition. Understanding their dynamics is thus essential for revealing the nature of phase transitions and critical phenomena [1].
Femtosecond noise correlation spectroscopy (FemNoC) enables real-time observation of magnetization fluctuations on the picosecond scale and has recently unveiled how they directly govern second-order phase transitions [2,3,4,5]. However, conventional FemNoC uses lock-in-based detection, which restricts the analysis to simple statistical operations and prevents more advanced statistical investigations.
To overcome this, we developed a digitizer-based FemNoC system that directly records every optical pulse, allowing flexible statistical processing. The sample was a canted antiferromagnet SmxEr1-xFeO3 (x = 0.72), which exhibits a second-order spin-reorientation transition near 320 K. Two-color femtosecond pulses probed the sample, transferring magnetization fluctuations to polarization fluctuations via the magneto-optical effect. The transmitted pulses were detected by two balanced amplified photodetectors, and polarization signals were digitized for statistical analysis, successfully capturing the magnetization fluctuation dynamics.
Femtosecond noise correlation spectroscopy (FemNoC) enables real-time observation of magnetization fluctuations on the picosecond scale and has recently unveiled how they directly govern second-order phase transitions [2,3,4,5]. However, conventional FemNoC uses lock-in-based detection, which restricts the analysis to simple statistical operations and prevents more advanced statistical investigations.
To overcome this, we developed a digitizer-based FemNoC system that directly records every optical pulse, allowing flexible statistical processing. The sample was a canted antiferromagnet SmxEr1-xFeO3 (x = 0.72), which exhibits a second-order spin-reorientation transition near 320 K. Two-color femtosecond pulses probed the sample, transferring magnetization fluctuations to polarization fluctuations via the magneto-optical effect. The transmitted pulses were detected by two balanced amplified photodetectors, and polarization signals were digitized for statistical analysis, successfully capturing the magnetization fluctuation dynamics.
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· 382 Publication: [1] P. C. Hohenberg, et al., Rev. Mod. Phys. 49, 435 (1977).
[2] M. A. Weiss, et al., Nat. Commun. 14, 7651 (2023).
[3] M. A. Weiss, et al., Rev. Sci. Instrum. 95, 083005 (2024).
[4] M. A. Weiss, et al., Phys. Rev. Appl. 24, 044021 (2025).
[5] M. A. Weiss, et al., arXiv:2509.26084 (2025).
Presenters
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Kohsuke Ataka
- Keio University