YBCO颗粒膜Josephson微桥结的高频响应  

HIGH-FREQUENCY RESPONSE OF JOSEPHSON MICRO-BRIDGE JUNCTION IN YBCO GRANULAR FILM

作　　者：徐勤军[1] AbbasA.Essa 马海霞[1] 徐克西[1] 鲍家善[1] 

机构地区：[1]上海大学物理系,上海201800

出　　处：《低温物理学报》2000年第3期187-194,共8页Low Temperature Physical Letters

摘　　要：在Aslamazov和Larkin给出的RSJ模型下电压时变方程无扰解的基础上 ,运用二阶微扰算法计算了Josephson结在高频辐射下的直流电压响应和阻抗 .结果表明 ,辐射响应正比于辐射功率 ,并且根据Josephson固有频率w0 是大于、等于、还是小于辐射频率w ,可将响应分为三个特性频率区 .当w大于或者小于w0 时 ,响应可以用V I特性参数表示 .当w0 w时 ,响应正比于 :(1 )直流特性曲线的斜率 .(2 )辐射频率的负二次方 .(3)本征Josephson振荡的电压幅值 .当w0 w时 ,响应正比于V I曲线的曲率 .我们的实验表明 ,当w0 w时 ,响应正比于辐射功率和V I特性曲线的曲率 .所得到的等效噪声功率为NEP =2 .45× 1 0 -1 4 W/Hz1 /2 ,明显优于常规的辐射热探测器 .For a current driven Josephson junction shunted by an Ohmic resistance , the dc voltage response and impedance to external high frequency currents is calculated with a second order perturbation method based on the unperturbed solution for the time evolution of the voltage as given by Aslamazov and Larkin. The response is proportional to signal power and has three characteristic frequency regions depending on whether the internal self generated Josephson frequency, w\-0 , is larger than, equal to, or smaller than the signal frequency, w . For w> or <w\-0 the response could be expressed by easily observable parameters of the dc voltage current characteristics. This permits comparison of the predictions with experimental results obtained on micro bridge junctions whose dc characteristics were only approximately represented by the simple model chosen for analysis. For w\-0w the response is found to proportional to (1) the slope of the dc characteristic, (2) the inverse square of the applied frequency, (3) the voltage amplitude of the inherent Josephson oscillations. For w\-0w the response is proportional to curvature. For w\-0～w occurrence of resonance response depends to a considerable degree on fluctuations of the average voltage. For w\-0w the results of our experiment is in reasonable agreement with the predictions of analysis. And the noise equivalent power we got is 2.45×10\+\{-14\}W/Hz\+\{1/2\}, which is much better than other types of bolometric detector.

关 键 词：YBCO 颗粒膜 高频响应 Josephson微桥结 

分 类 号：O511[理学—低温物理] O47[理学—物理]