【摘要】 采用电阻阻错结的无序二维约瑟夫森结阵列模型,数值研究超导薄膜中垂直磁场引起的涡旋运动.通过分析磁场激发产生的涡旋度Ne及低频电压噪声S0的变化特性,得到如下结论:在无序超导体中固定温度不变,随着磁场的减弱涡旋液态经过准有序的布拉格相,涡旋玻璃相重新进入到低磁场下的钉扎稀磁液相.由于在涡旋玻璃相中,电流驱动下的噪声值表现出一个峰,表明系统处于无序与有序相互竞争的亚稳态,并且临界电流应有峰值效应.计算得到噪声值的变化与Okuma等得到的无序超导MoxSi1-x膜实验现象一致,并能解释磁场降低引起的重新进入钉扎的稀磁液相行为.更多还原

【Abstract】 Using the resistively shunted junction model,we study magnetic-field-induced phase transitions of the vortex glass states in a disordered two-dimensional Josephson junction array.From calculated results of the vorticity of the vortex system and the voltage noise generated by current-driven vortices as a function of the magnetic field,the following conclusions can be drawn.1) With decreasing the magnetic field,the vortex system exhibits a reentrant transition from a vortex glass phase to a pinned dilute vortex liquid.2) There is a peak of voltage noise driven by the current in the vortex glass state.It follows that the system is in a sub-stable state as a result of the competition between ordered and disordered interactions,which results in peak effects of the critical current.The calculated results are consistent with recent experimental reports by Okuma and Kamada on disordered and superconducting Mo_xSi_ 1-x films.更多还原