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Effect of Te doping on superconductivity and charge-density wave in dichalcogenides 2H-NbSe2-xTex (x = 0, 0.1, 0.2)
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Single crystals of Te-doped dichalcogenides 2H-NbSe2-xTex (x ---- 0, 0.10, 0.20) were grown by vapour transport method. The effect of Te doping on the superconducting and charge-density wave (CDW) transitions has been investigated. The sharp decrease of residual resistance ratio, RRR = R(3OOK)/R(SK), with increasing Te content was observed, indicating that the disorder in the conducting plane is induced by Te doping. Meanwhile the superconducting transition temperature, Tc, decreases monotonically with Te content. However, the CDW transition temperature, TCDW, shown by a small jump in the temperature dependence of the resistivity near 30 K, increases slightly. The results show that the suppression of superconductivity might be caused by the enhancement of CDW ordering. The disorder has little influence on the CDW ordering. 相似文献
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Temperature dependence of the upper critical magnetic field (Hc2) near Tc of 20 K in a BaFe1.9 Ni0.1 As2 single crystal is determined via magneto-resistance measurements, for the out-plane (H ⊥ab) and in-plane (H || ab) directions in magnetic fields of up to 8 T. The upper critical fields at zero temperature estimated by the Werthamer-Helfand- Hohenberg (WHH) formula are μ0H^|| c2(0) = 137 T and μ0H⊥c2(0) = 51 T, both exceeding the weak-coupling Pauli paramagnetic limit (μ0Hp = 1.84Tc). However, the WHH formula could overestimate the μ0H^||12(0) value. The anisotropy of upper critical fields is around 3 in the temperature range close to Tc. The result is very similar to the Co-doped 122 superconductor BaFe2-x Cox As2, indicating that electron-doped 122 superconductors exhibit similar superconducting properties. 相似文献
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Using the nonequilibrium Keldysh Green's function technique, the Fano effect of a parallel-coupled triple Rashba quantum dot system is investigated. The conductance as a function of electron energy is numerically calculated. Compared with the case of a parallel-coupled double quantum dot system, two additional Fano resonance peaks occur in the conductance spectrum. By adjusting the structural parameters, the two Fano resonance peaks may change into the resonance peaks. In addition, the influence of Rashba spin-orbit interaction on the conductance is studied. 相似文献
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A series of Th and F co-doped superconductors Sm1-xThxFeAsO1-yFy are synthesized and the variation of superconductivity with the doping level is investigated. At the fixed Th doping level x = 0.1, the superconducting transition temperature Tc increases monotonically with F content, and finally Tc reaches a maximum of about 55K around y = 0.1, and saturates for even more F content the normal state thermopower increases monotonically with 'overdoped' regime is not observed and possible explanation (y = 0.15). Similar to the SmFeAsO1-y Fy system, the doping level. However the decrease of Tc in the is discussed. 相似文献
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真菌毒素具有荧光特性,因此可以用三维荧光光谱分析方法来检测真菌毒素浓度。在检测过程中,通过去除瑞利散射、平滑等光谱预处理后,采用平行因子算法(PARAFAC)建立回归模型,并由该模型依据待测样本的三维荧光光谱数据计算出真菌毒素的浓度。对一组含有不同浓度真菌毒素B1的白酒样本进行实验,结果表明:针对三维荧光光谱数据,由于掺杂的干扰比较多,进行光谱预处理可以提高建模效果;采用三维的PARAFAC建模方法效果要比常规的二维建模方法好;由于PARAFAC对组分数很敏感,所以建模过程中选择适当的组分数对模型的效果影响比较大。 相似文献
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现代光谱仪器强大的多维光谱数据产生能力使得多维光谱数据定量分析方法成为迫切需要研究的课题。针对多维光谱定量分析中的多维光谱数据以张量模式表达的特点,研究了基于支持张量机的多维光谱定量分析方法。该方法保留了多维光谱数据所固有的结构信息及数据的内在相关性,减少了模型中的待定模型参数,也克服了平行因子法、多维偏最小二乘等方法中需要预估组分数的缺点。对水体中化学耗氧量和总有机碳的检测进行了实验检验。实验结果表明:与现有的多维光谱定量分析方法比较,本方法提高了校正模型性能,并且模型对需预先确定的参数C和ε的变化不敏感。 相似文献
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微纳光纤是一种直径接近或小于传输光波长的纤维波导,由于纤芯和包层折射率差较大,具有强光场约束、强倏逝场、低损耗、反常波导色散、表面均匀性好和机械性能高等特性。近年来,以纳米材料作为饱和吸收体的被动锁模激光器成为超短脉冲激光技术方向的研究热点。得益于微纳光纤的强光场约束能力及大比例倏逝场,纳米材料与微纳光纤的复合结构能显著增强光与物质的相互作用,进而降低该复合结构的饱和吸收阈值,为超短脉冲产生和非线性动力学等研究提供一个新颖而灵活的平台。同时,微纳光纤因具有反常波导色散、光谱滤波、饱和吸收和偏振敏感等特性,在激光器的色散调控、偏振锁模等方面获得应用。介绍了微纳光纤的制备和特性以及在锁模激光方面的典型应用和相关技术的最新进展,并就未来的发展方向进行了展望。 相似文献
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采用PECVD技术在BK7玻璃基底上沉积了不同厚度的单层SiO2(折射率为1.46)和SiNx(折射率为1.84)光学薄膜,并对这2种膜层进行抗激光损伤阈值(LIDT)测试,分析讨论了PECVD技术制备的单层光学薄膜与抗激光损伤特性之间的关系。实验结果表明:PECVD技术制备的单层SiO2薄膜有较高的LIDT,薄膜光学厚度在o/4~o/2之间时,在光学厚度为350 nm时,LIDT有最小值21.7 J/cm2,光学厚度为433 nm时,LIDT有最大值27.9 J/cm2。SiNx薄膜的LIDT随着光学厚度增加而减小,在光学厚度为o/4时,LIDT有最大值29.3 J/cm2,光学厚度为o/2时,LIDT有最小值4.9 J/cm2。 相似文献
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