Y3Fe5O12(YIG)/Pt异质结构中基于超快自旋塞贝克效应产生太赫兹相干辐射研究

铁磁/非磁异质结构中的超快自旋流-电荷流转换实现相干太赫兹辐射得到了广泛研究.热自旋电子学结合了热输运与磁输运,可以有效地产生和探测自旋的非平衡输运.本文利用飞秒激光脉冲激发铁磁绝缘体钇铁石榴石(Y₃Fe₅O₁₂, YIG)/Pt异质结构,通过超快自旋塞贝克效应(SSE)产生太赫兹(THz)相干辐射.实验中, THz脉冲的相位随外加磁场和激光入射样品顺序的反转而反转,表明THz辐射与界面温度梯度的方向密切相关.为了考察界面对THz辐射性能的影响,系统地研究了YIG/Pt异质结构不同退火处理后的THz辐射情况.实验发现,生长在Gd₃Ga₅O₁₂(GGG)衬底上的YIG/Pt经退火处理后再原生一层Pt膜,其THz辐射强度提高了一个数量级.归因于退火后增强了YIG/Pt界面的自旋混合电导率.此外,还研究了生长在高阻Si衬底上退火后优化结构的能量密度与THz辐射强度的关系,拟合得到饱和能量密度约为1.4 mJ/cm².实验结果表明, YIG/...     

海藻多糖中硫酸基含量对抑制草酸钙晶体形成和修复受损伤肾小管上皮细胞的影响

采用X射线衍射法、傅里叶变换红外光谱仪、扫描电子显微镜、ζ电位仪和电感耦合等离子体发射光谱仪,比较了4种分子量相近(约3 700 Da)、但硫酸基(—OSO₃^-)含量不同的降解海藻多糖对草酸钙(CaC₂O₄)晶体生长的调控作用;采用细胞实验比较了它们对受损伤肾小管上皮细胞(HK-2)的修复能力。这4种海藻多糖分别是降解紫菜多糖(PY-1)、降解龙须菜多糖(GL-2)、降解羊栖菜多糖(SF-3)和降解裙带菜多糖(UP-4),其—OSO₃^-含量分别为17.9%、13.3%、8.2%和5.5%。结果表明,这4种多糖均能够抑制一水草酸钙(COM)生长,诱导二水草酸钙(COD)生成,增加溶液中可溶性Ca²⁺离子浓度,增加晶体表面的ζ电位绝对值,从而降低晶体的聚集程度;这些多糖均能修复被草酸氧化损伤的HK-2细胞,提高细胞活力和超氧化物歧化酶(SOD)活力,降低丙二醛(MDA)的释放量。结果表明,多糖中—OSO₃^-...     

基于工艺偏差的自旋转移矩辅助压控磁各向异性磁隧道结电学模型及其应用研究

自旋转移矩辅助电压调控磁各向异性磁隧道结(STT辅助VCMA-MTJ)作为非易失性全加器(NV-FA)中的核心部件,具有切换速度快、功耗低,稳定性好等优点,将在物联网、人工智能等领域具有良好的发展前景.然而随着磁隧道结(MTJ)尺寸的不断缩小以及芯片集成度的不断提高,工艺偏差对MTJ及NV-FA电路性能的影响将变得越来越显著.本文基于STT辅助VCMA-MTJ磁化动力学,在充分考虑薄膜生长工艺偏差以及刻蚀工艺偏差影响的情况下,建立了更为精确的STT辅助VCMA-MTJ电学模型,研究了上述两种工艺偏差对MTJ及NV-FA电路性能的影响.结果表明,当自由层厚度偏差γ_tf≥6%或氧化层厚度偏差γ_tox≥0.7%时,MTJ将无法实现状态切换;当隧穿磁阻率偏差β增大到30%时,读取裕度SM将下降高达17.6%.对于NV-FA电路,通过增大电压V_b1以及写‘0’时增大电压V_b2或写‘1’时减小V_b2,可有效降低非易失性加数写入错误率;通过增大逻辑运算驱动电压V_dd,可...     

Ultrafast Terahertz Probes of Charge Transfer and Recombination Pathway of CH_3NH_3PbI_3 Perovskites

We use transient terahertz photoconductivity measurements to demonstrate that upon optical excitation of CH_3NH_3PbI_3 perovskite, the hole transfer from CH_3NH_3PbI_3 into the organic hole-transporting material(HTM)Spiro-OMe TAD occurs on a sub-picosecond timescale. Second-order recombination is the dominant decay pathway at higher photo-excitation fluences as observed in neat CH_3NH_3PbI_3 films. In contrast, under similar experimental conditions, second-order recombination weakly contributes the relatively slow recombination between the electrons in the perovskite and the injected holes in HTM, as a loss mechanism at the CH_3NH_3PbI_3/Spiro-OMe TAD interface. Our results offer insights into the intrinsic photophysics of CH_3NH_3PbI_3-based perovskites with direct implications for photovoltaic devices and optoelectronic applications.     

Energy Transfer in the Light-Harvesting Complexes of Purple Bacteria

In this paper, we use a nonlinear decohering quantum model to study the initial step of photosynthesis which is an ultrafast transfer process of absorption the sunlight by light-harvesting complexes and electronic excitation transfer to the reaction center(RC). In this decohering model, the Hamiltonian of the system commutes with the systemenvironment interaction. We take B850 ring of light-harvesting complex II(LH-II) in purple bacteria as an example to calculate the efficiency of the energy transfer as a function of time. We find that the environmental noise can make the LH-II have stable energy transfer efficiency over a long time. This is to say that the environmental noise which is the decohering source has advantage of the energy transfer in the process of photosynthesis.     

激波诱导气流与液幕,液柱相经作用的实验研究

利用激波管对激波诱导气流与液幕,液柱的相互作用进行了实验研究。通过比较发现,这种相互作用下的液体块变形破碎过程与以往对于液滴进行的研究结果很不相。     

球偏差域和拟球

研究了空间球偏差域和拟球,证明了拟球一定量球偏差域,给出了球偏差域的一个充分必要条件。