标题： 由位移场驱动的过渡金属二硫化物中超导性与谷铁磁之间的转变 显示英文标题

标题： Displacement-Field-Driven Transition between Superconductivity and Valley Ferromagnetism in Transition Metal Dichalcogenides

摘要： 最近的实验在扭曲双层WSe$_2$在范霍夫填充附近观察到了超导性和相关磁性之间的转变，这是由位移场$D$驱动的。 受实验启发，我们从理论上提出了一种普遍机制，用于二维（2D）自旋轨道耦合六方系统中由$D$控制的超导性和铁磁性之间的转变，其中范霍夫奇点（VHS）位于费米能级上。 我们表明，这种转变可以通过一个仅包含范霍夫奇点的简单模型自然地捕捉到，而无需考虑费米面细节，在该模型中，控制费米面不稳定的互作用由$D$通过屏蔽库仑相互作用的带投影来调控。 通过使用超越平均场水平的重整化群技术处理这个简单模型，我们发现，在弱位移场$D<D_c$下，手性$d/p$波超导性自然占主导地位。 在更强的位移场$D>D_c$下，一个\textit{山谷铁磁相}(vFM) 取代了它，由于谷调制的磁化而具有空间非均匀性。 最后，我们讨论预测的超导性到铁磁性的转变在少层六方范德华材料系统丰富家族中发生的普遍条件。 以扭曲双层 WSe$_2$为例，我们讨论可以证伪我们预测的实验检测。 显示英文摘要

摘要： Recent experiments have observed transitions between superconductivity and correlated magnetism in twisted bilayer WSe$_2$ near van-Hove fillings, driven by the displacement field $D$. Motivated by the experiment, we theoretically propose a general mechanism for a $D$-controlled transition between superconductivity and ferromagnetism in two-dimensional (2D) spin-orbit-coupled hexagonal systems, where van Hove singularities (VHS) lie on the Fermi level. We show that such a transition can be naturally captured by a simple VHS-only model without Fermi surface details, where the inter-VHS interactions that govern the Fermi surface instabilities is controlled by $D$ through the band projection of screened Coulomb interaction. By treating this simple model with renormalization group technique beyond mean-field level, we find that a chiral $d/p$-wave superconductivity naturally dominates under a weak displacement field $D<D_c$. At a stronger displacement field $D>D_c$, a \textit{valley ferromagnetic phase} (vFM) takes over, which is spatially non-uniform due to valley-modulated magnetization. Finally, we discuss generic conditions for the predicted superconductivity-to-ferromagnetism transition to take place in the rich family of few-layer hexagonal van der Waals material systems. Taking twisted bilayer WSe$_2$ as a case study, we discuss experimental detections that can falsify our prediction.