论文标题
曲线涡流的非线性动力学和曲线涡流的耗散。
Nonlinear Dynamics and Dissipation of a Curvilinear Vortex Driven by a Strong Time-Dependent Meissner Current
论文作者
论文摘要
我们报告了在强的交流磁场$ h（t）= h \sinΩt$平行于表面的巨大的涡流线的大振幅振荡的数值模拟。通过考虑到非线性涡流线张力，涡流质量和非线性larkin-ovchinnikov（LO）粘性阻力系数$η（v）$，通过表面AC Meissner电流驱动的涡旋涡流段消散的功率。我们表明，与涡流速度$ v $的$η（v）$减少可以从根本上改变被困涡流引起的表面电阻$ r_i（h）$的场依赖性。在低频下，$ r_i（h）$以$ h $的形式表现出常规增加，但是随着$ω$的增加，表面电阻变成$ h $的非单调功能，在较高场上，$ h $降低了。计算了频率，引脚间距和平均自由路径$ L_I $对$ r_ {i}（h）$的字段依赖性的影响。结果表明，随着表面变得更脏，$ l_i $降低，$ r_ {i}（h）$的异常下降，$ h $转移到较低的磁场，这可能比较低的临界磁场小得多。我们的数值模拟还表明，使用$ v $的$η（v）$减少可能会在高场幅度和频率下导致涡旋弯曲不稳定性，从而导致沿涡流的动态扭结形成。 $ r_i（h）$ $ r_i（h）$由被垂直于表面的稀疏涡流引起的，可以提供机会调查由强电流密度驱动的极端非线性动力学，直到低温下达到降低极限。 $ r_i（h）$的行为可以通过改变射频频率或非磁性杂质的浓度来调整，而不会被DC或脉冲传输测量值的强加热效应掩盖。
We report numerical simulations of large-amplitude oscillations of a trapped vortex line under a strong ac magnetic field $H(t)=H\sinωt$ parallel to the surface. The power dissipated by an oscillating vortex segment driven by the surface ac Meissner currents was calculated by taking into account the nonlinear vortex line tension, vortex mass and a nonlinear Larkin-Ovchinnikov (LO) viscous drag coefficient $η(v)$. We show that the LO decrease of $η(v)$ with the vortex velocity $v$ can radically change the field dependence of the surface resistance $R_i(H)$ caused by trapped vortices. At low frequencies $R_i(H) $ exhibits a conventional increases with $H$, but as $ω$ increases, the surface resistance becomes a nonmonotonic function of $H$ which decreases with $H$ at higher fields. The effects of frequency, pin spacing and the mean free path $l_i $ on the field dependence of $R_{i}(H) $ were calculated. It is shown that, as the surface gets dirtier and $l_i$ decreases, the anomalous drop of $ R_{i}(H) $ with $H$ shifts to lower fields which can be much smaller than the lower critical magnetic field. Our numerical simulations also show that the LO decrease of $η(v)$ with $v$ can cause a vortex bending instability at high field amplitudes and frequencies, giving rise to the formation of dynamic kinks along the vortex. Measurements of $R_i(H)$ caused by sparse vortices trapped perpendicular to the surface can offer opportunities to investigate an extreme nonlinear dynamics of vortices driven by strong current densities up to the depairing limit at low temperatures. The behavior of $R_i(H)$ which can be tuned by varying the rf frequency or concentration of nonmagnetic impurities is not masked by strong heating effects characteristic of dc or pulse transport measurements.
