Magnetic Order Induced Suppression of Photoluminescence in van der Waals Magnet CrPS₄

On April 20^th, the journal Laser & Photonics Reviews published online a paper titled "Magnetic Order Induced Suppression of Photoluminescence in van der Waals Magnet CrPS₄" by Professor Qihua Xiong from Tsinghua University, a user of Wuhan National High Magnetic Field Center. This achievement was accomplished in collaboration with Academician Kai Chang from the Institute of Semiconductors, Chinese Academy of Sciences, and was supported by the pulsed high magnetic field facility of our university. Professor Weihang Zhou from the center, as well as Yichun Pan and Zheng Wang, doctoral students of the grade of 2021, provided magneto-optical measurements using flat-top pulsed high magnetic field.

In recent years, two-dimensional magnetic materials have attracted significant attention from researchers due to their great potential in applications of spintronics and optoelectronic devices. However, in practical applications, two-dimensional magnets not only face the challenge of air instability, but also encounter the challenge of insufficient understanding of the complex coupling effects between their magnetic order and electrons, phonons, and photons. As one of the few air-stable van der Waals magnets, CrPS₄, with its unique physical properties, provides an ideal platform for the study of spin-exciton coupling mechanism.

Figure 1. Photoluminescence spectra of CrPS₄ under pulsed high magnetic fields and magnetic order modulated radiative recombination of electron-hole pairs.

In this study, focusing on the air-stable van der Waals magnet CrPS₄, the authors systematically investigated its photoluminescence (PL) spectral characteristics under temperature, wavelength, and magnetic field-dependent conditions. They found that the PL peak intensity significantly decreased under the influence of an external magnetic field, revealing a strong magneto-optical coupling effect in the van der Waals magnet CrPS₄. Specifically, by combining experimental data from high magnetic field experiments with precise density functional theory (DFT) calculations, the authors provided the first evidence that magnetic order induces the formation of a large number of spin-forbidden dark excitons, leading to a significant reduction in exciton PL intensity. The PL emission primarily originates from the transition process from the 3d orbitals of Cr atoms to the 3p orbitals of S atoms. The darkening of electron-hole pairs induced by two-dimensional magnetic order may be a universal phenomenon in two-dimensional magnetic materials, highlighting the profound impact of magnetic order on optical selection rules. These findings not only reveal a universal spin-charge coupling effect but also provide an important theoretical foundation for a deeper understanding of how magnetic order in two-dimensional magnets regulates optical properties. Moreover, they highlight the broad prospects for developing advanced magneto-optoelectronic devices based on CrPS₄.

This study utilized the high-sensitivity magneto-optical measurement technique developed by the microscopic magneto-optics team in Wuhan National High Magnetic Field Center based on a 50T, 100ms long flat-top pulsed magnetic field (Chin. Phys. B (2025), DOI: 10.1088/1674-1056/adce95). This technique can increase the integration time for a single spectrum from the commonly used ~1ms in the pulsed field communities to the ~100ms level, thereby significantly enhancing the signal-to-noise ratio of the spectral data. The relevant experimental data provided strong support for this achievement.

Link: https://onlinelibrary.wiley.com/doi/full/10.1002/lpor.202400862