Skog Aiste, Hovhannisyan Razmik A, Krasnov Vladimir M
Department of Physics, Stockholm University, AlbaNova University Center, SE-10691 Stockholm, Sweden.
Nanomaterials (Basel). 2024 Oct 12;14(20):1634. doi: 10.3390/nano14201634.
The lack of dense random-access memory is one of the main obstacles to the development of digital superconducting computers. It has been suggested that AVRAM cells, based on the storage of a single Abrikosov vortex-the smallest quantized object in superconductors-can enable drastic miniaturization to the nanometer scale. In this work, we present the numerical modeling of such cells using time-dependent Ginzburg-Landau equations. The cell represents a fluxonic quantum dot containing a small superconducting island, an asymmetric notch for the vortex entrance, a guiding track, and a vortex trap. We determine the optimal geometrical parameters for operation at zero magnetic field and the conditions for controllable vortex manipulation by short current pulses. We report ultrafast vortex motion with velocities more than an order of magnitude faster than those expected for macroscopic superconductors. This phenomenon is attributed to strong interactions with the edges of a mesoscopic island, combined with the nonlinear reduction of flux-flow viscosity due to the nonequilibrium effects in the track. Our results show that such cells can be scaled down to sizes comparable to the London penetration depth, ∼100 nm, and can enable ultrafast switching on the picosecond scale with ultralow energy per operation, ∼10-19 J.
缺乏密集随机存取存储器是数字超导计算机发展的主要障碍之一。有人提出，基于单个阿布里科索夫涡旋（超导体中最小的量子化对象）存储的AVRAM单元能够实现向纳米尺度的大幅微型化。在这项工作中，我们使用含时金兹堡 - 朗道方程对此类单元进行了数值建模。该单元代表一个包含小超导岛、用于涡旋进入的不对称缺口、引导轨道和涡旋陷阱的磁通子量子点。我们确定了在零磁场下运行的最佳几何参数以及通过短电流脉冲可控操纵涡旋的条件。我们报告了超快速的涡旋运动，其速度比宏观超导体预期的速度快一个数量级以上。这种现象归因于与介观岛边缘的强相互作用，以及由于轨道中的非平衡效应导致的磁通流粘度的非线性降低。我们的结果表明，此类单元可以缩小到与伦敦穿透深度相当的尺寸，约100纳米，并且能够在皮秒尺度上实现超快速切换，每次操作的能量超低，约10^-19焦耳。
