Spin-Photon Coupling Effect In Chiral Organic Crystals

In recent years,the development of organic electronics has effectively promoted many types of organic functional devices,such as organic light-emitting diodes,organic solar cells,and organic field-effect transistors.At the same time,it has also stimulated the interest in spin,the intrinsic properties,of organic materials.At present,the strong electron-lattice coupling and weak spin-orbit interactions and hyperfine interactions of organic materials present more opportunities and challenges for studying the spin-related effects of organic materials.In organic spin devices,the spin state can be controlled by contact-type,such as electrical regulation,or non-contact,such as magnetic regulation or light regulation.Due to the high accuracy and low consumption,the light-controlled spins in organic materials have considerably development prospects,which are expected to be used in all-optical magnetic storage,3D imaging,and other fields to facilitate our lives.Compared with achiral materials,chiral materials have many unique optical properties,such as optical rotation,circular dichroism,and circularly polarized luminescence.Due to the lack of symmetry in the chiral structure,the coupling between the electronic spin angular momentum and the orbital angular momentum could be effectively increased,which allows photon-spin effects to exist in chiral materials,such as magneto-chiral dichroism and chiral-induced spin selectivity effect,etc.Chiral organic crystals have strong electro-phonon coupling and increased orbital angular momentum,which may be suitable for studying the coupling mechanism between photons and electron spins.Based on organic chiral crystals,this paper studies the process of photon-spin coupling in organic systems with experiments and theoretical simulations.1.Photon-regulated the orientation of spinBy constructing an organic charge transfer system,the spin spontaneous polarization in organic materials could be achieved,and preparing an organic ferromagnet without transition metal doping.Based on theoretical calculations and experimental data analysis,the key factors that determine the performance of organic chiral ferromagnetism can be summarized as follows:charge transfer,crystallization,and molecular configuration.Under the identical intensity,once the excitation light is switched from linearly polarized light to circularly polarized light,the magnetization and magnetoelectric coupling of the chiral charge transfer magnet are significantly increased,effectively realizing the regulation of spin states in organic chiral materials by polarized light.Moreover,this effect of light-controlled spin is closely related to the chiral-induced orbital angular momentum.2.Spin-regulated the polarization of photonsDue to the exchange interaction,spin-orbit coupling,and external magnetic field effect,the phenomenon that spin regulates light polarization can be observed in magneto-optical crystals.In traditional organic materials,the orbital angular momentum is so weak that could be ignored,therefore,it is hard for spins to adjust the polarization state of light through the channel of spin-orbital-photon.By preparing chiral organic materials,chiral-induced orbital angular momentum could be introduced in organic systems,spin-photon coupling may be observed.We have grown chiral organic crystals to study the effect of chiral-induced orbital angular momentum on spin-photon coupling.Among them,the orbital angular momentum generated by chirality may cause the splitting of the LUMO and affect the spin relaxation time of the material.Through applying a magnetic field,the splitting of the energy level will be further changed to demonstrate the novel magneto-optical phenomena.At the same time,effective spin relaxation will cause circularly polarized luminescence in chiral organic crystals.The photon-spin coupling in organic chiral crystals provides significantly possibilities for the preparation of organic spin functional devices.The research content of this article is expected to promote the application of organic materials in the spin optical detection,optical magnetic storage,3D imaging and other fields as well as lay the foundation for my future research work.