A groundbreaking discovery in the field of nonlinear optical effects has been made by a research team led by Professor Sheng Zhigao at the Hefei Institutes of Physical Science of the Chinese Academy of Sciences. The team has successfully observed the strong nonlinear magnetic second harmonic generation (MSHG) induced by the ferromagnetic order in monolayer CrPS4, marking a significant advancement in the field of optical materials.
Second harmonic generation (SHG) is a nonlinear optical effect that is sensitive to symmetry breaking in materials. Traditionally, SHG has been observed in crystals with broken symmetry (i type), but its occurrence in magnetic systems (c type) has been limited and much weaker. This has constrained its potential applications in optical devices. The discovery of strong nonlinear magnetic second harmonic generation in monolayer CrPS4 opens up new possibilities for utilizing magnetic two-dimensional van der Waals materials in optoelectronics.
In their study, Professor Sheng’s team explored the magnetic order-related SHG effects in the two-dimensional antiferromagnetic material CrPS4. Interestingly, they found that while the antiferromagnetic order in bulk and even-layered CrPS4 did not produce any c type SHG effects, a substantial c type SHG effect was induced by monolayer ferromagnetic order in odd-layered CrPS4. This observation marks the first instance of ferromagnetic order induced c type SHG effects in a 2D magnet under the electric-dipole approximation, a result of the dual breaking of spatial and time inversion symmetries.
One of the most significant findings of the research is that the ferromagnetic order induced c type SHG in monolayer CrPS4 has a signal strength comparable to that of i type SHG, which is derived from the breaking of crystal structural symmetry. This level of signal strength is unprecedented among all known magnetic materials, highlighting the unique properties and potential applications of two-dimensional magnetic materials in the field of nonlinear optics.
The discovery of strong nonlinear magnetic second harmonic generation in monolayer CrPS4 represents a major breakthrough in the study of nonlinear optical effects in magnetic materials. The research findings hold promise for the development of novel optical devices and applications, as well as further exploration of the intricate relationship between magnetic order and nonlinear optical properties in two-dimensional materials.
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