Valley Carrier Dynamics in Monolayer Molybdenum Disulphide from Helicity Resolved Ultrafast Pump-probe Spectroscopy

We investigate the valley related carrier dynamics in monolayer MoS2 using helicity resolved non-degenerate ultrafast pump-probe spectroscopy at the vicinity of the high-symmetry K point under the temperature down to 78 K. Monolayer MoS2 shows remarkable transient reflection signals, in stark contrast to bilayer and bulk MoS2 due to the enhancement of many-body effect at reduced dimensionality. The helicity resolved ultrafast time-resolved result shows that the valley polarization is preserved for only several ps before scattering process makes it undistinguishable. We suggest that the dynamical degradation of valley polarization is attributable primarily to the exciton trapping by defect states in the exfoliated MoS2 samples. Our experiment and a tight-binding model analysis also show that the perfect valley CD selectivity is fairly robust against disorder at the K point, but quickly decays from the high-symmetry point in the momentum space in the presence of disorder.Comment: 15 pages,Accepted by ACS Nan

Competing Magnetic Orderings and Tunable Topological States in Two-Dimensional Hexagonal Organometallic Lattices

The exploration of topological states is of significant fundamental and practical importance in contemporary condensed matter physics, for which the extension to two-dimensional (2D) organometallic systems is particularly attractive. Using first-principles calculations, we show that a 2D hexagonal triphenyl-lead lattice composed of only main group elements is susceptible to a magnetic instability, characterized by a considerably more stable antiferromagnetic (AFM) insulating state rather than the topologically nontrivial quantum spin Hall state proposed recently. Even though this AFM phase is topologically trivial, it possesses an intricate emergent degree of freedom, defined by the product of spin and valley indices, leading to Berry curvature-induced spin and valley currents under electron or hole doping. Furthermore, such a trivial band insulator can be tuned into a topologically nontrivial matter by the application of an out-of-plane electric field, which destroys the AFM order, favoring instead ferrimagnetic spin ordering and a quantum anomalous Hall state with a non-zero topological invariant. These findings further enrich our understanding of 2D hexagonal organometallic lattices for potential applications in spintronics and valleytronics.Comment: 9 pages, 8 figure

Kerr nonlinearity induced strong spin-magnon coupling

One pillar of quantum magnonics is the exploration of the utilization of the mediation role of magnons in different platforms to develop quantum technologies. The efficient coupling between magnons and various quantum entities is a prerequisite. Here, we propose a scheme to enhance the spin-magnon coupling by the magnonic Kerr nonlinearity in a YIG sphere. We find that the Kerr-enhanced spin-magnon coupling invalidates the widely used single-Kittel-mode approximation to magnons. It is revealed that the spin decoherence induced by the multimode magnons in the strong-coupling regime becomes not severe, but suppressed, manifesting as either population trapping or persistent Rabi-like oscillation. This anomalous effect is because the spin changes to be so hybridized with the magnons that one or two bound states are formed between them. Enriching the spin-magnon coupling physics, the result supplies a guideline to control the spin-magnon interface

4,4′-Di-3-pyridyl-2,2′-dithio­dipyrimidine

The asymmetric unit of the title compound, C18H12N6S2, contains one half-mol­ecule situated on a twofold rotational axis that passes through the mid-point of the S—S bond. In the mol­ecule, the C—S—S—C torsion angle is 81.33 (7)°. The crystal packing exhibits no significantly short inter­molecular contacts

Introduction to the wheelchair training's influence on the rehabilitation of patients

目的  通过轮椅训练提高患者掌握轮椅的技巧，保证患者乘坐轮椅时的安全，提高患者日常生活能力及社会参与能力。方法  通过轮椅基本技术动作练习、轮椅技巧动作训练、轮椅体育项目训练、社会实践检测。结果  患者轮椅训练前后对照，躯干的控制能力较前好转，ADL能力明显提高，社会参与能力增强。结论  轮椅训练可以使残疾人参与康复体育和社会活动的机会明显增加。Objective: Training to improve patient’s master of wheelchair technology to ensure the safety of patients in wheelchairs things to improve patients' daily living skills and social participation skills. Methods: By practicing basic techniques wheelchair, wheelchair technology movement training, wheelchair sports training, social practice test. Results: Wheelchair patients before and after control technology, the ability to control the trunk before it gets better, ADL ability as well as social participation improved significantly. Conclusion: Wheelchair training increased opportunities for people with disabilities to participate in the rehabilitation of sports and social activities.

{Bis[4-(2-pyrid­yl)pyrimidin-2-yl]sulfane}dichloridocobalt(II)

The asymmetric unit of the title compound, [CoCl2(C18H12N6S)], contains one half-mol­ecule situated on a twofold rotation axis which passes through the Co and S atoms. The metal centre is in a distorted octahedral CoCl2N4 coordination with the Cl atoms in the axial positions. In the crystal structure, inter­molecular C—H⋯Cl inter­actions help to establish the packing