Photoluminescence Path Bifurcations by Spin Flip in Two-Dimensional CrPS4

Magnetic Field Tunable Polaritons in the Ultrastrong Coupling Regime in CrSBr

Collective excitations of bound electron-hole pairs, i.e., excitons, are ubiquitous in condensed matter systems, and it has been shown that they can strongly couple to other degrees of freedom, such as spin, orbital, and lattice. Among van der Waals materials with pronounced excitonic responses, CrSBr has attracted significant interest due to a very large energy shift of its fundamental bright exciton (at 1.36 eV) under an external magnetic field. This effect has been associated with an increased interlayer electronic hopping when the magnetic order is switched from antiferromagnetic to ferromagnetic by an external magnetic field, enabling its optical detection. In this work, we report the observation of a second bright excitonic resonance (at 1.76 eV), displaying a 5-fold enhancement of the magnetically induced energy shift to ∼100 meV, which we associate to a decreased spatial localization and increased interband nature compared to the fundamental exciton. Moreover, we show how the light-matter interaction reaches the ultrastrong regime where this exciton hybridizes with the cavity modes of photons confined to CrSBr flakes, forming polaritons with a Rabi splitting of ℏΩR ≃ 372 meV, of the same order of magnitude as the one reported for the first exciton. These results expand the understanding of the relationship between the optical response and band structure of CrSBr and clarify the essential ingredients for optimizing magneto-electronic coupling for applications.

Evidence of Strong Orbital-Selective Spin-Orbital-Phonon Coupling in CrVO_{4}

Coupling of orbital degree of freedom with a spin exchange, i.e., Kugel-Khomskii-type interaction (KK), governs a host of material properties, including colossal magnetoresistance, enhanced magnetoelectric response, and photoinduced high-temperature magnetism. In general, KK-type interactions lead to deviation in experimental observables of coupled Hamiltonian near or below the magnetic transition. Using diffraction and spectroscopy experiments, here we report anomalous changes in lattice parameters, electronic states, spin dynamics, and phonons at four times the Néel transition temperature (T_{N}) in CrVO_{4}. The temperature is significantly higher than other d-orbital compounds such as manganites and vanadates, where effects are limited to near or below T_{N}. The experimental observations are rationalized using first-principles and Green's function-based phonon and spin simulations that show unprecedentedly strong KK-type interactions via a superexchange process and an orbital-selective spin-phonon coupling coefficient at least double the magnitude previously reported for strongly coupled spin-phonon systems. Our results present an opportunity to explore the effect of KK-type interactions and spin-phonon coupling well above T_{N} and possibly bring various properties closer to application, for example, strong room-temperature magnetoelectric coupling.

Advances in the two-dimensional layer materials for cancer diagnosis and treatment: unique advantages beyond the microsphere

In recent years, two-dimensional (2D) layer materials have shown great potential in the field of cancer diagnosis and treatment due to their unique structural, electronic, and chemical properties. These non-spherical materials have attracted increasing attention around the world because of its widely used biological characteristics. The application of 2D layer materials like lamellar graphene, transition metal dichalcogenides (TMDs), and black phosphorus (BPs) and so on have been developed for CT/MRI imaging, serum biosensing, drug targeting delivery, photothermal therapy, and photodynamic therapy. These unique applications for tumor are due to the multi-variable synthesis of 2D materials and the structural characteristics of good ductility different from microsphere. Based on the above considerations, the application of 2D materials in cancer is mainly carried out in the following three aspects: 1) In terms of accurate and rapid screening of tumor patients, we will focus on the enrichment of serum markers and sensitive signal transformation of 2D materials; 2) The progress of 2D nanomaterials in tumor MRI and CT imaging was described by comparing the performance of traditional contrast agents; 3) In the most important aspect, we will focus on the progress of 2D materials in the field of precision drug delivery and collaborative therapy, such as photothermal ablation, sonodynamic therapy, chemokinetic therapy, etc. In summary, this review provides a comprehensive overview of the advances in the application of 2D layer materials for tumor diagnosis and treatment, and emphasizes the performance difference between 2D materials and other types of nanoparticles (mainly spherical). With further research and development, these multifunctional layer materials hold great promise in the prospects, and challenges of 2D materials development are discussed.