Superconductivity in CuIr2-xAlxTe4 telluride chalcogenides

The relationship between charge-density-wave (CDW) and superconductivity (SC), two vital physical phases in condensed matter physics, has always been the focus of scientists' research over the past decades. Motivated by this research hotspot, we systematically studied the physical properties of the layered telluride chalcogenide superconductors CuIr$_{2-x}$Al$_{x}$Te$_{4}$ ($0 \leqslant x \leqslant 0.2$). Through the resistance and magnetization measurements, we found that the CDW order was destroyed by a small amount of Al doping. Meanwhile, the superconducting transition temperature ($T_{\rm c}$) kept changing with the change of doping amount and rose towards the maximum value of 2.75 K when $x=0.075$. The value of normalized specific heat jump ($\Delta C/\gamma T_{\rm c}$) for the highest $T_{\rm c}$ sample CuIr$_{1.925}$Al$_{0.075}$Te$_{4}$ was 1.53, which was larger than the BCS value of 1.43 and showed the bulk superconducting nature. In order to clearly show the relationship between SC and CDW states, we propose a phase diagram of $T_{\rm c}$ vs. doping content.     

城市环境下基于地理位置自适应的车载网络路由协议

针对城市车载自组织网络环境中节点分布不平衡,信号传输被障碍物遮挡,目标节点不断移动等问题,提出一个适合城市环境基于地理位置信息的自适应路由协议SAGR(Self-Adaptive Geographic Routing for city environments in vehicular network).SAGR通过远程混合模式被动路由机制SAGR-RM和局部定向受限泛洪路由机制SAGR-LM,将路由过程分成两个层次,增强了路由协议的健壮性以及对目标位置的容错性.通过NS-2软件仿真分析了SAGR协议的性能,结果表明SAGR比现有的基于位置路由协议在数据包传输、端到端延迟和路由开销方面等都有显著的改进.     

1T-NbSeTe电子结构的角分辨光电子能谱

过渡金属二硫族化物因其广泛存在超导、电荷密度波等新奇的物理现象成为了近些年来凝聚态物理研究中的一大热点,同时这也为研究超导和电荷密度波等电子序之间的相互作用提供了典型的材料体系.本文利用角分辨光电子能谱对1T结构的NbSeTe单晶进行系统的研究,揭示了其电子结构.沿高对称方向的能带测量发现, 1T-NbSeTe布里渊区M点附近存在一个范霍夫奇点,能量位于费米能以下约250 meV处.对能带色散的仔细分析发现该体系中没有明显电子-玻色子(声子)耦合带来的能带扭折.基于上述实验结果,对过渡金属二硫族化物中电荷密度波和超导的产生以及1T-NbSeTe中电荷密度波和超导被抑制的可能原因进行了讨论.