Enhanced conductivity and weakened magnetism in Pb-doped Sr_(2)IrO_(4)

Group IV element Pb has been selected as the dopant to dope at the Sr site of Sr_(2)IrO_(4). It is exciting to find that the single-phase crystal structure could be maintained with a high Pb doping level of up to x=0.3 in Sr_(2-x)Pb_(x)IrO_(4). The mapping data obtained from energy-dispersive x-ray spectroscopy analyses give solid evidence that the Pb ions are uniformly distributed in the Sr_(2)IrO_(4) matrix. The incorporation of Pb leads to a moderate depression of the canted antiferromagnetic ordering state. The electrical conductivity could be greatly enhanced when the Pb doping content is higher than x=0.2.The present results give a fresh material base to explore new physics in doped Sr_(2)IrO_(4) systems.

High-Performance Visible Light Photodetector Based on BiSeI Single Crystal

The continuing demand for new optoelectronic devices drives researchers to seek new materials suitable for photodetector applications.Recently,ternary compound semiconductors have entered researchers’field of vision,among which chalcohalides have attracted special interest because of their rich properties and unique crystal structure consisting of atom chains and inter-chain van der Waals gaps.We have synthesized high-quality BiSeI single crystals with[110]-plane orientation and fabricated a photodetector.The optoelectronic measurements show a pronounced photocurrent signal with outstanding technical parameters,namely high responsivity(3.2 A/W),specific detectivity(7×10^(10) Jones)and external quantum efficiency(622%)for λ=635 nm,V_(ds)=0.1 V and P_(opt)=0.23 mW/cm^(2).The high performance of BiSeI photodetector and its layer structure make it a promising candidate for low-dimensional optoelectronic applications.

自然通风模式及光伏透过率对双层皮幕墙冬季运行特性影响研究

通过搭建实验装置,实测封闭模式、日间自然通风模式及中午自然通风模式下双层皮幕墙的运行参数,研究自然通风模式及光伏透过率对双层皮幕墙冬季运行特性的影响.实验结果表明:三种通风模式下内层皮温度、传导热流密度和辐射热流密度差异较小,说明通风模式对室内得热量基本无影响;日间部分时间段空腔顶部温度高于20℃,合理选择自然通风时间可同时为室内提供热量和新风;且日间自然通风模式更有利于提高发电功率.光伏材料可改善双层皮幕墙的保温性能,并大幅度降低冬季室内得热量.

添加剂对青藏高原不同成熟期异燕麦青贮发酵特性的影响

为有效利用青藏高原当地牧草资源解决冬季饲料短缺问题,对异燕麦(Helictotrichon virescens Henr.)的青贮发酵进行了研究。异燕麦在抽穗/开花期收获,在阳光充足的条件下萎蔫,切碎,在小袋筒仓中抽真空,在室温(5℃~15℃)下储存60d。青贮饲料在不使用(CK)或使用本地乳酸菌(LAB)接种剂(IN1)、商业乳酸菌接种剂(IN2)和苯甲酸钠(BL)的情况下进行处理。与开花期相比,抽穗期异燕麦对照青贮饲料中乳酸和乙酸含量较高(P<0.05),pH、丁酸和氨氮水平较低(P<0.05)。与对照相比,添加剂在青贮过程中通过抑制酵母菌、需氧菌和大肠菌群来提高(P<0.05)有氧稳定性。特别是,本地LAB接种剂增加了(P<0.05)青贮饲料中乳酸盐、乙酸盐和丙酸盐的浓度,并降低了丁酸盐和氨氮的浓度。本研究证实,本地乳酸菌接种剂可以提高异燕麦的青贮品质,异燕麦可能是青藏高原上牦牛等动物的潜在冬季饲料。

Unusual Normal and Superconducting State Properties Observed in Hydrothermal Fe_(1-δ)Se Flakes

The electronic and superconducting properties of Fe_(1-δ)Se single-crystal flakes grown hydrothermally are studied by the transport measurements under zero and high magnetic fields up to 38.5 T.The results contrast sharply with those previously reported for nematically ordered Fe Se by chemical-vapor-transport(CVT)growth.No signature of the electronic nematicity,but an evident metal-to-nonmetal crossover with increasing temperature,is detected in the normal state of the present hydrothermal samples.Interestingly,a higher superconducting critical temperature T_c of 13.2 K is observed compared to a suppressed T_c of 9 K in the presence of the nematicity in the CVT Fe Se.Moreover,the upper critical field in the zero-temperature limit is found to be isotropic with respect to the field direction and to reach a higher value of-42 T,which breaks the Pauli limit by a factor of 1.8.

Non-Stoichiometry Effects on the Extreme Magnetoresistance in Weyl Semimetal WTe2

Non-stoiehiometry effect on the extreme magnetoresistanee is systematically investigated for the Weyl semimetal WTe2. Magnetoresistance and Hall resistivity are measured for the as-grown samples with a slight difference in Te vacancies and the annealed samples with increased Te vacancies. The fits to a two-band model show that the magnetoresistanee is strongly dependent on the residual resistivity ratio （i.e., the degree of non-stoichiometry）, which is eventually understood in terms of electron doping that not only breaks the balance between electron-type and hole-type carrier densities, but also reduces the average carrier mobility. Thus the compensation effect and ultrahigh mobility are probably the main driving force of the extreme magnetoresistance in WTe2.

Transient Photoconductivity in LaRhO3 Thin Film

High-quality epitaxial LaRhO3(LRO) thin films on SrTiO3(110) single-crystalline substrates are fabricated by pulsed laser deposition and their photoconductivity properties are studied. The transient photoconductivity(TPC) effect is found in this semiconductor LRO film at room temperature. The magnitude of TPC increases almost linearly with the laser power intensities and the photon energies in visible light range. Moreover, the difference in the TPC results under two airflow conditions confirms that both intrinsic photoinduced carrier accumulation and extrinsic photoinduced heating effects contribute to the magnitude of TPC effect.

Transforming a Two-Dimensional Layered Insulator into a Semiconductor or a Highly Conductive Metal through Transition Metal Ion Intercalation

Atomically thin two-dimensional(2D) materials are the building bricks for next-generation electronics and optoelectronics, which demand plentiful functional properties in mechanics, transport, magnetism and photoresponse.For electronic devices, not only metals and high-performance semiconductors but also insulators and dielectric materials are highly desirable. Layered structures composed of 2D materials of different properties can be delicately designed as various useful heterojunction or homojunction devices, in which the designs on the same material(namely homojunction) are of special interest because preparation techniques can be greatly simplified and atomically seamless interfaces can be achieved. We demonstrate that the insulating pristine ZnPS_3, a ternary transition-metal phosphorus trichalcogenide, can be transformed into a highly conductive metal and an n-type semiconductor by intercalating Co and Cu atoms, respectively. The field-effect-transistor(FET) devices are prepared via an ultraviolet exposure lithography technique. The Co-ZnPS_3 device exhibits an electrical conductivity of 8 × 10^(4) S/m, which is comparable to the conductivity of graphene. The Cu-ZnPS_3 FET reveals a current ON/OFF ratio of 1-05 and a mobility of 3 × 10^(-2 )cm^(2)·V^(-1)·s^(-1). The realization of an insulator, a typical semiconductor and a metallic state in the same 2D material provides an opportunity to fabricate n-metal homojunctions and other in-plane electronic functional devices.

Field-induced anisotropic magnetic phase transitions and tricritical phenomena in GdCr_(6)Ge_(6)

The interaction between complex magnetic structures and non-trivial band structures in ternary rare-earth GdCr_(6)Ge_(6) induces exotic and abundant electro-magnetic phenomena.In this work,we perform a systematical investigation on critical behaviors and magnetic properties of the single-crystal GdCr_(6)Ge_(6).The temperature,field,and angle dependence of magnetization unveils strong magnetic anisotropy along the c-axis and isotropic characteristic in the ab-plane.Critical exponentsβ=0.252(1),γ=0.905(9),δ=4.606(3)for H//ab,andβ=0.281(3),γ=0.991(8),δ=4.541(5)for H//c are obtained by the modified Arrott plot method(MAP)and critical isotherm(CI)analysis.The determined exponents for both directions are consistent with the theoretical prediction of a tricritical mean-field model.Based on detailed magnetization measurements and universality scaling,comprehensive magnetic phase diagrams of GdCr6Ge6for H//ab and H//c are constructed,which reveal that the external field induces a ferromagnetic(FM)transition for H//ab while a ferrimagnetic(FIM)one for H//c.Two tricritical points are determined for H//ab(11.2 K,266.3 Oe)and H//c(11.3 K,3.3 kOe)on the phase diagrams,respectively.The field-induced anisotropic magnetic configurations and multiple phases are clarified,where the moments of Gd and Cr form FM coupling for H//ab while FIM one for H//c via the interaction between Gd and Cr sublattices.

Photophysical and electrical properties of organic waveguide nanorods of perylene-3,4,9,10-tetracarboxylic dianhydride

The single crystalline nanostructure of organic semiconductors provides a very promising class of materials for applications in modern optoelectronic devices. However, morphology control and optoelectronic property modulation of high quality single crystalline samples remain a challenge. Here, we report the morphology-controlled growth of single crystalline nanorod arrays of perylene- 3,4,9,10-tetracarboxylic dianhydride （IrFCDA）. We demonstrate that, unlike FTCDA film, PTCDA nanorods exhibits optical waveguide features, enhanced absorption, and Frenkel excitation emission in the visible region. Additionally, we measured the electrical properties of PTCDA nanorods, including the conductivity along the growth direction of the nanorod, which is roughly 0.61 S-m i （much higher than that of pure crystalline PTCDA films）.

基于中学物理“问题·实验·深度思维”的研究

文章研究目的为强化中学物理“问题·实验·深度思维”模式应用,探索教学实践新路径,促进中学物理教学质量不断提高和发展。研究路径为“双基”阶段,强调基本知识和技能,重视基础教学;“三维”阶段,强化过程教学,培养科学态度;“四素”阶段,培养必备品格和关键能力,树立正确的价值观。文章研究结论是,创建“问题·实验·深度思维”发展研究,有助于中学物理教学高质量发展。