Coherent quantum phase slip

A hundred years after the discovery of superconductivity, one fundamental prediction of the theory, coherent quantum phase slip (CQPS), has not been observed. CQPS is a phenomenon exactly dual to the Josephson effect; whereas the latter is a coherent transfer of charges between superconducting leads, the former is a coherent transfer of vortices or fluxes across a superconducting wire. In contrast to previously reported observations of incoherent phase slip, CQPS has been only a subject of theoretical study. Its experimental demonstration is made difficult by quasiparticle dissipation due to gapless excitations in nanowires or in vortex cores. This difficulty might be overcome by using certain strongly disordered superconductors near the superconductor-insulator transition. Here we report direct observation of CQPS in a narrow segment of a superconducting loop made of strongly disordered indium oxide; the effect is made manifest through the superposition of quantum states with different numbers of flux quanta. As with the Josephson effect, our observation should lead to new applications in superconducting electronics and quantum metrology.     

聚甲基乙撑碳酸酯的交联

利用过氧化物过氧化二异丙苯（DCP）和多官能团化合物三烯丙基异氰尿酸酯（TAIC），对聚甲基乙撑碳酸酯（PPC）进行了交联研究。研究发现，DCP和TAIC的用量对PPC的交联均有较大影响，PPC交联后，其凝胶含量、机械性能、弹性模量、玻璃化转变温度均有所增加，1％的DCP和4％的TAIC用量可得到较理想的交联PPC材料。