论文标题
$φ_0$ -Josephson在扭曲的双层石墨烯中，由山谷极化状态诱导
$φ_0$-Josephson junction in twisted bilayer graphene induced by a valley-polarized state
论文作者
论文摘要
最近，对魔术角扭曲双层石墨烯（MATBG）中的栅极定义的约瑟夫森连接进行了实验研究，并观察到高度非常规的Fraunhofer模式。在这项工作中，我们表明，连接MATBG两个超导区域的互动驱动的山谷极化状态将导致长期持久的纯电力控制$φ_0$结点，其中两个超导体在基地状态下获得有限相位差$φ_0$。我们指出，$φ_0$ - 结的出现源于山谷极化状态，它破坏了时间反转对称性和三角形翘曲效应，破坏了Interavalley反转对称性。重要的是，连接处的空间不均匀的山谷极化阶参数可以解释实验中观察到的高度非常规的弗劳恩霍夫模式。我们的工作探讨了山谷偏振状态的新型运输特性，并表明栅极定义的MATBG Josephson交界处可以意识到第一个纯电力控制的$φ_0$ junctions，并在超导设备中进行了应用。
Recently, gate-defined Josephson junctions in magic angle twisted bilayer graphene (MATBG) were studied experimentally and highly unconventional Fraunhofer patterns were observed. In this work, we show that an interaction-driven valley-polarized state connecting two superconducting regions of MATBG would give rise to a long-sought-after purely electric controlled $φ_0$-junction in which the two superconductors acquire a finite phase difference $φ_0$ in the ground state. We point out that the emergence of the $φ_0$-junction stems from the valley-polarized state which breaks time-reversal symmetry and trigonal warping effects which break the intravalley inversion symmetry. Importantly, a spatially non-uniform valley polarization order parameter at the junction can explain the highly unconventional Fraunhofer patterns observed in the experiment. Our work explores the novel transport properties of the valley-polarized state and suggests that gate-defined MATBG Josephson junctions could realize the first purely electric controlled $φ_0$-junctions with applications in superconducting devices.
