Spin-induced linear polarization of photoluminescence in antiferromagnetic van der Waals crystals

Abstract

Antiferromagnets display enormous potential in spintronics owing to its intrinsic nature, including terahertz resonance 1,2 , multilevel states 3,4 , and absence of stray fields 5,6 . Combining with the layered nature, van der Waals (vdW) antiferromagnets hold the promise in providing new insights and new designs in twodimensional (2D) spintronics. The zero net magnetic moments of vdW antiferromagnets strengthens the spin stability, however, impedes the correlation between spin and other excitation elements, like excitons 7,8 . Such coupling is urgently anticipated for fundamental magneto-optical studies and potential opto-spintronic devices. Here, we report an ultra-sharp excitonic emission with excellent monochromaticity in antiferromagnetic nickel phosphorus trisulfides (NiPS3) from bulk to atomically thin flakes. We prove that the linear polarization of the excitonic

Electronic Raman scattering in the 2D antiferromagnet NiPS 3

“…In all the spectra under different laser excitations, a peak can be resolved at the same position ~1.39 eV, exhibiting a distinct feature of photoluminescence (PL). This peak could be assigned to the phonon sideband of the coherent Zhang-Rice exciton, which results in an ultrasharp and linear-polarized emission at low temperature ( 9 , 10 ). In contrast, the other two peaks, labeled as R 1 and R 2 , exhibit an obvious redshift with the decrease of the excitation energy and, finally, disappear when the excitation energy is below ~2.35 eV.…”

“…To confirm this, the electronic band structure and density of states for bulk NiPS 3 were calculated using first-principle density functional theory (DFT) + U method with U = 4.0 eV (see fig. S3) ( 6 , 7 , 9 ). The calculated band structure clearly shows the near-flat electronic bands near the conduction band minimum, which are predominantly contributed by Ni d orbitals (see fig.…”

“…This result suggests a weak thickness dependence on the magnetic transition of NiPS 3 from bulk down to a four-layer region, which is in a good agreement with the previous result revealed by Raman spectroscopy ( 6 ). Considering the insensitivity of d-d transition to the spin ordering, the anisotropic ER response may be the consequence of the anisotropic absorption of incident photons due to the magnetic linear dichroism of materials, of which polarization degree is at the same order as ER response ( 9 , 10 , 48 ).…”

“…Electronic Raman (ER) scattering, where photons are scattered by electronic excitations in the materials, has been used in revealing the electronic behaviors in low-dimensional materials, such as metallic carbon nanotubes and AlGaAs epilayers ( 25 , 26 ). NiPS 3 exhibits a unique electronic structure with a highly localized electronic band composed by d orbitals ( 9 , 27 ), suggesting a potential to explore the d-d transitions in 2D systems using ER spectroscopy.…”

Multiwavelength magnetic coding of helical luminescence in ferromagnetic 2D layered CrI3

“…Alternatively, air-stable metallic 2D vdW CrTe 2 and CrSe 2 with thickness-dependent magnetic orders have been directly synthesized by chemical vapor deposition (CVD) methods ( Li et al., 2021 ; Meng et al., 2021 ). However, thus far, few 2D vdW magnets have been revealed luminescence and exciton behaviors, and none examining magnetic coding of photoluminescence (PL), despite the discovery of luminescence in FM CrI 3 and AFM NiPS 3 ( Hwangbo et al., 2021 ; Kang et al., 2020 ; Seyler et al., 2017 ; Wang et al., 2021 ). Moreover, the PL of CrI 3 derives from a ligand-field-allowed d-d transition, which naturally leads to a very broad PL peak with an FWHM of 100–200 nm owing to strong vibrionic coupling ( Seyler et al., 2017 ), extremely limiting the potential for photonic devices; in addition, it is difficult to achieve magnetic/electric control of spin in AFM NiPS 3 , due to a high critical field up to 10 T at least ( Wang et al., 2021 ).…”