Transport characteristics of ramp-type YBa2Cu3O7-δ/PrBa2Cu3O7-y/YBa2Cu3O7-δ Josephson junctions

The transport behaviors of YBa2Cu3O7-δ/PrBa2Cu3O7-y/YBa2Cu3O7-δ junctions with barrier thickness ranging from 6 to 30 nm were studied. In these junctions, the existence of a proximity layer was confirmed by the appearence of a temperature-dependent coherence length. The structure of the junctions changed from SNS to SNINS with increasing barrier thickness. It was found that the quasiparticles transport through a thin barrier by metallic conduction and through a thick barrier by tunneling conduction. In junctions with a moderate barrier thickness, we found a subgaplike feature in the conductance-voltage curves, which could be related to multiple Andreev reflection in a SNcNS Josephson junction. For junctions with a thick barrier, the dependence of conductance on temperature could be well fitted by the T4/3 law. This suggested that the quasiparticles transport across a thick PrBa2Cu3O7-y barrier layer via two localized states in an inelastic tunneling process.published_or_final_versio

Large Extra Dimension effects through Light-by-Light Scattering at the CERN LHC

Observing light-by-light scattering at the Large Hadron Collider (LHC) has received quite some attention and it is believed to be a clean and sensitive channel to possible new physics. In this paper, we study the diphoton production at the LHC via the process $\rm pp\rightarrow p\gamma\gamma p\rightarrow p\gamma\gamma p$ through graviton exchange in the Large Extra Dimension (LED) model. Typically, when we do the background analysis, we also study the Double Pomeron Exchange (DPE) of $\gamma\gamma$ production. We compare its production in the quark-quark collision mode to the gluon-gluon collision mode and find that contributions from the gluon-gluon collision mode are comparable to the quark-quark one. Our result shows, for extra dimension $\delta=4$, with an integrated luminosity $\rm {\cal L} = 200 fb^{-1}$ at the 14 TeV LHC, that diphoton production through graviton exchange can probe the LED effects up to the scale $\rm M_S=5.06 (4.51, 5.11) TeV$ for the forward detector acceptance $\xi_1 (\xi_2, \xi_3)$, respectively, where $0.0015<\xi_1<0.5$, $0.1<\xi_2<0.5$ and $0.0015<\xi_3<0.15$.Comment: 25 pages. 7 figs. Change some grammatical error

Interfacial microstructures in ramp type multilayer Josephson junctions studied by TEM

The microstructures of high Tc ramp type Josephson junctions were studied by using transmission electron microscopy. The work was emphasized at the interfacial defects and the influence of the ramp slope. The results show that for the ramp slope angles of 15°~40°, the epitaxy was still remained through all layers at the ramp region without the formation of big grain boundaries. No amorphous layers and secondary phases were observed at the barrier interfaces. For a gentle ramp junction, small misoriented grains appeared in some portions of the barrier. The substrate ramp formed during the ion etching process had little influence on the growth of the upper layers. In junctions with a steep ramp, defects increased near the interface, although the epitaxy of the barrier was of good quality. The results demonstrate that the slope angle of the junction ramp is an important factor that influences the performance of the Josephson junctions.published_or_final_versio

Preparation of continually graded barriers of YPrBaCuO for HTS Josephson junctions

We report preparation of a novel barrier structure for high Tc superconducting multilayer Josephson junctions using a simple composite target technique. Such a barrier consists of Yx Pr1-xBa2Cu3Oy with a continually varied concentration of yttrium. In this barrier no lattice mismatch and other incompatibility problems occur between adjacent layers. Thus the formation of interfacial defects and structural strain can be mostly prevented. The Josephson coupling takes place at the electrically formed interfaces rather than the structural interfaces. A particular feature of these junctions is that the effective thickness of the barrier strongly depends on the measuring temperature and the concentration gradient. The absence of the structural interface in the weak link region greatly enhances the reproducibility and the performance of these junctions.published_or_final_versio

Two granitic plutions in middle Western Kunlun Belt: their ages and possible sources

对西昆仑中带２个重要岩体进行了年代学和同位素示踪方面的研究。单颗粒锆石U-Pb 测年结果表明，库地北岩体（４０４Ｍａ）形成于加里东末期的一次岩浆活动；而阿卡阿孜山岩体中二长花岗岩２１５ Ｍａ的年龄则表明原被整个划入海西期的岩体实际上至少包括一部分印支期的岩浆活动。Sｍ／Ｎｄ同位素数据表明这２个花岗岩的源区并不均一，有地壳物质的加入且不排除壳幔混合成因的可能性。published_or_final_versio

Petrochemistry and mineral chemistry studies on metamorphic ultramafic rocks in Yanghou area, Zhenghe Country, Fujian Province, China

Petrochemistry studies indicate that the Yanghou metamorphic ultramafic rocksare composed of metamorphosed harzburgite and burgite and ultramafic cumulate . Trace element geochemistry and mineral chemistry studies on the metamorphosed harzburgite indicate that it is the relict of the depleted mantle. From systematic studies on petrochemistry , mineral chemistry and geochronology, it s concluded that the Yanghou metamorphic ultramafic rocks are components of Later Sinian-Early Paleozoic ophiolite in South China.岩石化学研究表明, 洋后变质超镁铁岩是由变质方辉橄榄岩和变质超镁铁堆积岩组成。变质方辉橄榄岩的微量元素地球化学及矿物化学特征表明, 应为亏损的残余地慢产物。通过系统的岩石地球化学、矿物化学及年代学研究, 认为洋后变质超镁铁岩可能为华南晚震旦一早古生代的蛇绿岩组成部分。published_or_final_versio

下地壳及壳慢过渡带化学不均一性 -- 河北汉诺坝地区深源捕虏体元素地球化学证据

河北汉诺坝玄武岩中长英质麻粒岩、镁铁质麻粒岩和辉石岩捕虏体的主量元素和微量元素特征, 反映了下地壳及壳鳗过渡带组成具有高度化学不均一性。不相容元素原始地慢标准化曲线特征的差异表明捕虏体成因复杂。MgO 与不相容元素无或仅有很弱的相关性, 与相容元素的相关性则相对较明显。这些特征反映了下地壳及壳慢过渡带存在较强和多元的混合作用。捕虏体的加权平均值比基于麻粒岩地体资料估算的下地壳平均组成偏基性, 揭示了二者可能的成因差异。The major and trace element data of granulite and pyroxenite xenoliths, which are entrained in Hannuoba basalt Hebei Province, North China, suggest the highly chemical heterogeneity in the lower crust and crust-mantle transitional zone. There is no or only POor linear correlation between MgO and incompatible elements. Whereas a bit remarked correlations are observed between MgO and most compatible elements.The geochemical characteristics suggest that the strong and multiple mixing processes may have Occurred universally both in the lower crust and crust-mantle transitional zone. The weighed average composition of xenoliths shows a more mafic composition of the lower crust than that estimated from granulite data, which may imply the difference in the genesis.published_or_final_versio

High-Tc ramp-type Josephson junctions with a continually graded Y1–xPrxBa2Cu3Oy barrier

High-Tc Josephson junctions with a graded barrier have been prepared by using a composite target. Such a barrier is synthesized by utilizing Y1–xPrxBa2Cu3Oy with a continually graded concentration of Pr, in which no lattice mismatch and other incompatible problems take place. The structural interfaces are absent in the weak link region and Josephson coupling occurs at the naturally formed superconducting/normal interfaces within the Y1–xPrxBa2Cu3Oy layer. Thus, it can significantly enhance the reproducibilty and performance of these junctions. The temperature dependences of the barrier thickness and Josephson were also studied. © 2001 American Institute of Physics.published_or_final_versio

Sr, Nd Pb isotopic characteristics of granulite and pyroxenite xenoliths in Hannuoba basalts, Hebei Province, and their implications for geologic processes

Rb-Sr, Sm-Nd and Pb isotopic systematics are reported for granulite and pyroxenite xenoliths in Hannuoba basalts, Hebei Province. The isotopic characteristics of xenoliths suggest t hat they might have formed recently , although there is no strict constraint on the precise age. The decoupling of low Rb/Sr and high [87]Sr/[86]Sr ratios implies the multi-stage evolution history and strong mixing processes. There are close ties between granulite and pyroxenites with different mineral assemblages on the Sr-Nd, Pb-Sr and Pb-Nd correlation figures. The granulite is the common end-member o f the three kinds o f pyroxenite. Combined with the distribution of the xenoliths in space and their isotopic relationships, It is proposed that delamination can be well used to explain the ties.系统研究了河北汉诺坝玄武岩中二辉麻粒岩和辉石岩捕虏体的Sr、Nd、Pb 同位素特征。虽然未确定捕虏体的形成时代, 但同位素特征显示它们可能为较近期( 中生代以来) 形成。低的Rb/Sr 与高 的[87]Sr/[86]Sr 比值的解耦表明捕虏体的形成经历了较强的混合作用。在二元同位素相关图上, 三类具不同矿物组成的辉石岩与二辉麻粒岩有密切关系, 即二辉麻粒岩投点位置是三类辉石岩的共同端点。综合考虑捕虏体的空间分布及其在Sr 、Nd、Pb 同位素协变图上的关系, 可以认为层离作用可较好地解释这些现象。published_or_final_versio