论文标题
非中心对称超导体/铁磁性多层的无野外超导二极管效应
Field-free superconducting diode effect in noncentrosymmetric superconductor/ferromagnet multilayers
论文作者
论文摘要
二极管效应是电子设备的基础,广泛用于整流器和AC-DC转换器。然而,在低温下,常规的半导体二极管具有高电阻率,可在操作过程中产生能量损失和加热。超导二极管效应(SDE)依赖于超导体中的反转对称性的损坏可能会减轻这一障碍:在一个方向上,零抗性超电流可以流过二极管,但是对于当前流动的相反方向,该设备以正常状态带有阻力。磁场的应用可以在具有极性结构的NB/V/TA超晶格中诱导SDE,在具有固定中心的不对称图案的超导装置中,或者在具有诱导涡旋的超导体/超导/铁磁杂交设备中。对外部磁场的需求限制了其实际应用。最近,在NBSE2/NB3BR8/NBSE2连接中观察到了无现场的SDE,它源自由NB3BR8屏障和相关的NBSE2/NB3BR8接口引起的非对称约瑟夫森隧道。在这里,我们使用非中心对称[nb/v/co/v/ta] 20多层提出了另一个实现零场SDE。磁性层提供必要的对称性破坏,我们可以通过调整结构参数(例如组成元素,膜厚度,堆叠顺序和重复数量)来调整SDE。我们通过铁磁层的磁化方向来控制SDE的极性。作为这项工作中使用的结构,人为堆叠的结构尤其引起人们的关注,因为它们与微加工技术兼容,并且可以与Josephson交界器等设备集成。因此,这项工作中介绍的无能损的SDE可能会使新型的非易失性记忆和逻辑电路具有超低功耗。
The diode effect is fundamental to electronic devices and is widely used in rectifiers and AC-DC converters. At low temperatures, however, conventional semiconductor diodes possess a high resistivity, which yields energy loss and heating during operation. The superconducting diode effect (SDE), which relies on broken inversion symmetry in a superconductor may mitigate this obstacle: in one direction a zero-resistance supercurrent can flow through the diode, but for the opposite direction of current flow, the device enters the normal state with ohmic resistance. The application of a magnetic field can induce SDE in Nb/V/Ta superlattices with a polar structure, in superconducting devices with asymmetric patterning of pinning centres, or in superconductor/ferromagnet hybrid devices with induced vortices. The need for an external magnetic field limits their practical application. Recently, a field-free SDE was observed in a NbSe2/Nb3Br8/NbSe2 junction, and it originates from asymmetric Josephson tunneling that is induced by the Nb3Br8 barrier and the associated NbSe2/Nb3Br8 interfaces. Here, we present another implementation of zero-field SDE using noncentrosymmetric [Nb/V/Co/V/Ta]20 multilayers. The magnetic layers provide the necessary symmetry breaking and we can tune the SDE by adjusting the structural parameters, such as the constituent elements, film thickness, stacking order, and number of repetitions. We control the polarity of the SDE through the magnetization direction of the ferromagnetic layers. Artificially stacked structures, as the one used in this work, are of particular interest as they are compatible with microfabrication techniques and can be integrated with devices such as Josephson junctions. Energy-loss-free SDEs as presented in this work may therefore enable novel non-volatile memories and logic circuits with ultralow power consumption.