Researchers from the Chinese Academy of Sciences have made a breakthrough discovery in the field of two-dimensional magnetic materials, unveiling the extraordinary magnetic second harmonic generation (MSHG) effect in monolayer CrPS₄. This finding paves the way for advancements in optoelectronics and opens new avenues for exploring the interplay between magnetism and optical properties in 2D materials.
Decoding 2D Matter with Magnetic Spin
Two-dimensional (2D) materials are class of materials much studied by the research community for their unique properties and capacity in diverse applications. In this plethora of 2D wonders, magnetic materials are particularly intriguing because they would allow us to couple electronic and magnetic functionalities on the nanoscale.
Now, however, a team of scientists led by Professor Sheng Zhigao at the Hefei Institutes of Physical Science of the Chinese Academy of Sciences believe they have made a breakthrough discovery. The research group has directly discovered the appearance of strong nonlinear magnetic second harmonic generation (MSHG) under ferromagnetic order created in monolayer CrPS₄, a 2D magnetic material. This discovery marks a huge step forward in our knowledge of how magnetism and optical properties intertwine… — Picture courtesy of the University at Buffalo
Uncovering the Mysteries of Second Harmonic Generation
One of the nonlinear optical effects is second harmonic response (SHR) which arises from a process of generating light at twice its original frequency by light-matter interaction. Whereas transient reflectivity is very sensitive on the other hand can provide access to a door to symmetry breaking in materials and, hence it is a very versatile tool for studying different material.
One set of examples are the crystals with broken symmetry (type i) and magnetic system (type c), where SHG was observed traditionally. Nevertheless, this class of SHG is generally quite weak to be beneficial as the inner working of an optical instrument.
This illuminates why this phenomenon works, the researchers note. They observed that, in bulk and monolayer CrPS₄, the antiferromagnetic order fails to exhibit any type c SHG effects. In CrPS₄, a significant type c SHG effect was found in the odd-layered sample due to the ferromagnetic state of the monolayer.
To the best of our knowledge, this corresponds to a type c under electric-dipole approximation (EDA) SHG from 2D magnet with runtime and spatial inversion symmetry breaking. Most importantly, they discovered that the ferromagnetic order-induced type c SHG has an intensity as strong as type i (nonlinear symmetry breaking of crystal structures) SHG. This is very unusual for all known magnetic materials.
Conclusion
This is a major discovery in 2D magnetic materials because this observation of large magnetic SHG raises significant implications of the SHG technique in revealing new properties of thin TMDs, or 2D magnets. This discovery does not only provide a better understanding of the correlation between magnetism and optical properties but also opens up possibilities towards high-end optoelectronic device applications. Their research makes it possible to study the exotic properties and potential applications of 2D magnetic materials in additional future technologies.
