Interplay between magnetism and superconductivity in 2D van der Waals heterostructures

超导态和时间反演对称性破缺态之间的相互作用允许非常规的超导性。我们打算探讨由超导和非超导货车范德华系统组合而成的各种二维货车范德华异质结构中邻近感应超导的性质。特别令人感兴趣的是新形式的库珀配对，特别是三重配对，由传统的s波超导体与磁性系统或更一般地说，具有破碎的空间和时间反转对称性的系统的邻近耦合产生。 我们建议制备由货车德瓦耳斯异质结构形成的垂直和横向约瑟夫森结。最近，我们已经证明，这样的系统可以表现出新的属性，包括约瑟夫森二极管效应，其中临界超电流密度的电流在相反的方向流动可以变化高达80%。 我们已经证明了这样的效果在约瑟夫森结（JJ）的势垒形成的货车德瓦尔斯半金属NiTe 2，PtTe 2和WTe 2使用超导电极形成的二维伊辛超导体2 H-NbSe 2以及传统的铌。二极管效应的详细起源仍有待确定。 我们计划通过探索二极管效应与使用各种2D材料形成的异质结构的详细电子和磁性结构的关系来解决这个问题。 我们还建议探索使用二维磁系统形成的异质结构中的邻近诱导超导性，该系统与二维超导材料结合，表现出拓扑非共线自旋纹理（例如skyrmions）。 这些系统中出现的超导态将使用磁输运技术以及超导隧道显微镜（STM）和超导隧道光谱（STS）来探索它们的空间范围。 一个重要的目标是理解和控制三重态对邻近诱导超导态的贡献。将使用分子束外延和机械剥离技术形成货车范德华异质结构。我们已经证明了分子束外延生长的高品质的货车范德华薄膜显示几个铁电性能薄如一个单一的原子层，也作为横向单层异质结构。我们的提案直接涉及SP 2244- 2010中“集体和相关现象（包括自旋、磁性和超导邻近效应、莫特绝缘体）以及2D vdW [异质]结构中出现的新型拓扑状态”的研究领域。 设想与SPP内的几个小组在理论和实验方面进行强有力的合作。

The interplay between superconducting states and states with broken time-reversal symmetry allows for unconventional superconductivity. We propose to explore the nature of proximity induced superconductivity in various 2D van der Waals heterostructures formed from combinations of superconducting and non-superconducting van der Waals systems. Of particular interest are novel forms of Cooper pairing, especially triplet pairing, engendered by proximity coupling of a conventional s-wave superconductor with magnetic systems or, more generally, systems with broken space and time reversal symmetries. We propose to prepare both vertical and lateral Josephson junctions formed from van der Waals heterostructures. Recently we have demonstrated that such systems can exhibit novel properties including a Josephson Diode Effect in which the critical supercurrent density for current flowing in opposite directions can vary by up to 80%. We have demonstrated such effects in Josephson Junctions (JJs) where the barrier is formed from the van der Waals semimetals NiTe2, PtTe2 and WTe2 using superconducting electrodes formed from both the 2D Ising superconductor 2H-NbSe2 as well as conventional niobium. The detailed origin of the diode effect remains to be determined. We plan to address this by exploring the relationship of the diode effect to the detailed electronic and magnetic structures of heterostructures formed using a wide variety of 2D materials. We also propose to explore proximity induced superconductivity in heterostructures formed using 2D magnetic systems that exhibit topological non-collinear spin textures (e.g. skyrmions) in combination with 2D superconducting materials. The emergent superconducting states in these systems will be explored using both magneto-transport techniques as well as superconducting tunneling microscopy (STM) and superconducting tunneling spectroscopy (STS) to explore their spatial extent. An important goal is to both understand and control the contribution of triplet pairing to the proximity induced superconducting states. Van der Waals heterostructures will be formed using both molecular beam epitaxy and mechanical exfoliation techniques. We have demonstrated the MBE growth of high-quality van der Waals films displaying several ferroic properties as thin as a single atomic layer and also as lateral monolayer heterostructures. Our proposal directly addresses the research area on “collective and correlated phenomena (including spin, magnetic and superconducting proximity effects, Mott insulators) and novel topological states emerging in 2D vdW [hetero]structures” in the SP 2244-2DMP. Strong collaborations with several groups within the SPP in both theory and experiment are envisaged.