磁通运动的电压噪声频谱分析和动力学相变

Spectrum analysis of voltage noise of moving vortex lattice and dynamic phase transition

用Langevin分子动力学方法模拟磁通运动的纵向电压噪声谱随磁场和电流的变化.计算结果表明,外加磁场增大到磁通运动动力学相变场FP,电压噪声谱中低频宽带噪声减小而出现洛伦兹形高频窄带噪声.外加磁场增大到熔化场Fm附近,高频窄带噪声峰值增高,峰值对应频率增大.在外加电流增强到磁通弹性运动区域,高频窄带噪声频谱呈现搓衣板形式.搓衣板高频窄带噪声产生于磁通平移速度的周期性调制,它表明层状超导体中运动的磁通格子存在有平移序的BG相.

Using Langevin molecular dynamics method, we have studied the voltage noise spectrum generated by current-driven vortices as a function of the magnetic field and current. It is found that the broad band noise (BBN) at low frequencies decreases with increasing magnetic field, it decreases at the magnetic field near the vortex dynamic transition field F-p, and the Lorentze narrow band noise (NBN) at high frequencies appears. As the magnetic field increases near the melting field F, the NBN peak goes up and shifts towards higher frequencies. In the elastic motion region of vortices with strong driving currents, NBN exhibits the washboard-like shape. This behavior arises from the periodic modulation of the translational velocity of vortices, suggesting that there is a Bragg glass phase with the translation order in the vortex lattices of the layered superconductors.