Direct Observation of the Linear Dichroism Transition in Two-Dimensional Palladium Diselenide

Abstract

The linear dichroism (LD) transition within anisotropic photonic materials displays promising prospects for applications in polarization-wavelength-selective detectors, optical switching, and optical communication. In conventional two-dimensional (2D) anisotropic materials, the LD is predominantly uniaxial over a broad spectrum of wavelengths and arises principally from the reduced symmetry of the materials. However, the LD transition behavior in crystalline 2D materials remains elusive. Here, we demonstrate the observation of a unique LD conversion phenomenon at a wavelength of 472 nm in palladium diselenide (PdSe2) using polarization-resolved absorption spectroscopy. This material exhibits prominent anisotropic responses and a high absorption ratio of α y /α x ≈ 1.11 at 364 nm, 1.15 at 532 nm, and 0.84 at 633 nm. We propose that this abnormal LD conversion behavior originates from the forceful localization rules at different parallel energy bands that exist within this material. Furthermore, the robust periodicity of Ag and B1g modes in polarization-resolved Raman spectroscopy is in good agreement with the theoretical structure symmetry analysis. This indicates the strong intrinsic LD effect in the anisotropic nature of PdSe2, which offers a macrolevel determination of crystal orientations. Such unique LD conversion features, in combination with strong LD effects, enable the air-stable PdSe2 to be a potential candidate for technological innovations in multispectral imaging, sensing, and polarization-sensitive and wavelength-controllable photoelectronic applications.

In-Plane Anisotropic Thermal Conductivity of Low-Symmetry PdSe2

“…Notably, this low-symmetry structure offers new characteristics for in-plane anisotropy in optics and electronics [16,17]. For example, PdSe 2 possesses a strong linear dichroism ratio, up to 1.9, which can act as a high polarization-sensitive photodetector [18,19]. Notably, both chemical vapor deposition (CVD) grown and exfoliated PdSe 2 exhibit extremely high air quality stability and device performance stability, which provides an excellent opportunity for future large-scale electronic device applications [20,21].…”

Giant Nonlinear Optical Activity in Two-Dimensional Palladium Diselenide

“…Because of the significant shifts of low-frequency Raman modes, the layer number can be determined precisely. The feasibility and specific operation of such results have been reported in detail in the previous works of authors [21].…”

“…After that, their TPA was measured using a nonlinear transmittance method. According to our previous reports, PdSe2 exhibits novel linear dichroism features under the excitation of 300-800 nm [21]. When the excitation wavelength is 800 nm, the linear absorption is almost negligible in the solid film.…”

“…Interestingly, PdSe2 is a novel pentagonal 2D material with robust anisotropy, high carrier mobility, and air stability, which gives it considerable advantages in nonlinear optoelectronic devices [20]. In addition, PdSe2 has a modifiable thickness-dependent bandgap from 0.03 to 3 1.37 eV [21], filling the interspace between zero-gap graphene and large-gap TMDCs.…”

Electric field induced giant valley polarization in two dimensional ferromagnetic WSe2/CrSnSe3 heterostructure

“…Among many two-dimensional (2D) materials for valleytronics, mostly the transition metal dichalcogenide (TMD) systems have been explored. For instance, the TMDs such as MoS 2 , MoSe 2 , WS 2 , and WSe 2 have broken inversion symmetry in the odd number of layer structures whereas the inversion symmetry is preserved in the even number of layer structure [7][8][9][10] . Usually, the odd number of layer TMD materials have a strong spin-orbit coupling (SOC) effect in the valence bands due to the lack of inversion symmetry, and this SOC effect is mostly observed for Group 6 of TMD materials 11 .…”