All-inorganic cesium lead halide perovskite nanocrystals have been widely investigated as promising materials for light and display. The primary challenge for their practical application is development of highly efficient and...

We study the strain tuning of magnetism in Mn doped MoS2 monolayer system. With the increase of the tensile strain, the magnetic ground state changes from a state with total magnetic moment Mtot =1.0 B to another state with Mtot =3.0 B for single doping in a 4 × 4 supercell. Physical mechanism is elucidated from the effects of the local bonding and geometry symmetries on orbital hybridization. In addition, we find the ferromagnetic coupling is favored for small distances between Mn atoms corresponding to the uniform doping concentration of 25%. More importantly, the ferromagnetic state is highly stable and robust to tensile strains. Therefore, diluted magnetic semiconductors can be obtained and the strain engineering should be a very promising approach to tune the magnetic moments.

The iridate Na2IrO3 was proposed to be a realization of the Kitaev model with a quantum spin liquid ground state. Experiments have now established that this material hosts a zigzag antiferromagnetic order. However, the previous assignment of the ordered moment direction to the a axis is controversial. We examine the magnetic moment direction of Na2IrO3 using the local spin density approximation plus spin orbit coupling+U calculations. Our calculations reveal that the total energy is minimized when the zigzag-ordered moments are aligned along g≈a+c direction. The dependence of the total energy on moment directions can be explained by adding anisotropic interactions to the nearest-neighbor Kitaev-Heisenberg model, on which the spin-wave spectrum is also calculated. The revision of ordered moments is very important to understanding and achieving possible exotic electronic phases in this compound.

While benefiting greatly from electronics, our society also faces a major problem of electronic waste, which has already caused environmental pollution and adverse human health effects. Therefore, recyclability becomes a must-have feature in future electronics. Here, we demonstrate an erasable and recreatable two-dimensional electron gas (2DEG), which can be easily created and patterned by depositing a water-dissolvable overlayer of amorphous Sr3Al2O6 (a-SAO) on SrTiO3 (STO) at room temperature. The 2DEG can be repeatedly erased or recreated by depositing the a-SAO or dissolving in water, respectively. Photoluminescence results show that the 2DEG arises from the a-SAO–induced oxygen vacancy. Furthermore, by gradually depleting the 2DEG, a transition of nonlinear to linear Hall effect is observed, demonstrating an unexpected interfacial band structure. The convenience and repeatability in the creation of the water-dissolvable 2DEG with rich physics could potentially contribute to the exploration of next generation electronics, such as environment-friendly or water-soluble electronics.

The Kitaev model of spin-1/2 on a honeycomb lattice supports degenerate topological ground states and may be useful in topological quantum computation. Na2IrO3 with honeycomb lattice of Ir ions have been extensively studied as candidates for the realization of the this model, due to the effective J eff = 1/2 low-energy excitations produced by spin-orbit and crystal-field effect. As the eventual realization of Kitaev model has remained evasive, it is highly desirable and challenging to tune the candidate materials toward such end. It is well known external pressure often leads to dramatic changes to the geometric and electronic structure of materials. In this work, the high pressure phase diagram of Na2IrO3 is examined by first-principles calculations. It is found that Na2IrO3 undergoes a sequence of structural and magnetic phase transitions, from the magnetically ordered phase with space group C2/m to two bond-ordered non-magnetic phases. The low-energy excitations in these high-pressure phases can be well described by the J eff = 1/2 states.

Most theoretical investigations about titanium oxide clusters focus on (TiO2)n. However, many TinOm clusters with ≠ 2 are produced experimentally. In this work, firstprinciples calculations are performed to probe the evolution of TinOm clusters. Our investigations show that for n=3-11, there exist one relatively stable specie; while for n=12-18, there are two relatively stable species: Ti-rich and O-rich species. HOMO-LOMO calculations show that the gap can be tuned by changing the size and configurations of TinOm clusters. Our investigation provides insights into the evolution of cluster-to-bulk process in titanium oxide.

needed to excite the electrons from the ground state to the conduction band. However, this strict requirement for highenergy photonic sources which is easily to pose great threat to human body limits their popularity in civil scenes. By comparison, visible light (≈400-700 nm) is harmless to our skin or eyes. In addition, the blue chip based white light emitting diodes are common light sources in nowadays human life. [6] Thus, it is a trend to promote the development of persistent phosphors which can be excited by the visible light. It is worth noting that some persistent phosphors can absorb light with low photon energy such as deep-red or near-infrared (NIR) so that accelerate the release process of trapped electrons, which is the wellknown photostimulation process. [1d] But it is different from the energy storage process (that is photoexcitation), and the latter will be discussed carefully in this paper. To date, some phosphors have been reported to realize the visible light storage and achieved commercial success, such as SrAl 2 O 4 : Eu 2+ , Dy 3+ (green), [7] CaAl 2 O 4 : Eu 2+ , Nd 3+ (blue), [8] Sr 2 MgSi 2 O 7 : Eu 2+ , Dy 3+ (azure), [9] Y 2 O 2 S: Mg 2+ , Ti 4+ , Eu 3+ (red). [10] In addition, Pan et al. have designed Zn 3 Ga 2 Ge 2 O 10 : Cr 3+ in 2011, in which the NIR afterglow can be induced by almost all visible light wavelength. [11] Bessière et al. have proposed a deep-red emissive phosphor ZnGa 2 O 4 : Cr 3+ in 2014, [12] which further enrich the luminous band of afterglow materials.Persistent phosphor, as an eco-friendly energy storage material, usually needs high-energy photonic rays in the storage process, such as ultraviolet (UV) light, X-ray, or even γ-ray. This strict requirement for light source which is harmful to human health greatly limits the popularity of persistent phosphors in the daily life. Here, a novel broadband orange persistent emissive phosphor LiGaO 2 :1%Mn 2+ (LGOM) is reported which supports efficient wide band excitation from UV to green light. The afterglow excited by 470 nm light even reaches ≈80% as intensity as UV excitation. The afterglow of LGOM excited by common blue lamp (450-460 nm) can be pictured by the smart phones for more than 48 h. The mechanism of visible light storage is discussed through the thermal-luminescence measurements. In addition, interestingly, its persistent emissive color can shift from orange-yellow to orange-red after ceasing the excitation source. This unique broadband orange afterglow phosphor which supports efficient wide range visible-light excitation, afterglow color shift, and long-lasting luminescence is expected to have potential applications in the fields of emergency direction, anticounterfeiting, decoration design, etc.

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