The emergence of a topological superconducting state in van der Waals heterostructures provides a new platform for exploring novel strategies to control topological superconductors. In particular, impurities in van der Waals heterostructures, generically featuring a moiré pattern, can potentially lead to the unique interplay between atomic and moiré length scales, a feature absent in generic topological superconductors. Here we address the impact of nonmagnetic impurities on a topological moiré superconductor, both in the weak and strong regime, considering both periodic arrays and single impurities in otherwise pristine infinite moiré systems. We demonstrate a fine interplay between impurity-induced modes and the moiré length, leading to radically different spectral and topological properties depending on the relative impurity location and moiré lengths. Our results highlight the key role of impurities in van der Waals heterostructures featuring moiré patterns, revealing the key interplay between length and energy scales in artificial moiré systems.

Twisted graphene multilayers provide tunable platforms to engineer flat bands and exploit the associated strongly correlated physics. The two-dimensional nature of these systems makes them suitable for encapsulation by materials that break specific symmetries. In this context, recently discovered two-dimensional helimagnets, such as the multiferroic monolayer NiI2, are specially appealing for breaking time-reversal and inversion symmetries due to their nontrivial spin textures. Here we show that this spin texture can be imprinted on the electronic structure of twisted bilayer graphene by proximity effect. We discuss the dependence of the imprinted spin texture on the wave-vector of the helical structure, and on the strength of the effective local exchange field. Based on these results we discuss the nature of the superconducting instabilities that can take place in helimagnet encapsulated twisted bilayer graphene. Our results put forward helimagnetic encapsulation as a powerful way of designing spin-textured flat band systems, providing a starting point to engineer a new family of correlated moire states.

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Unconventional superconductors represent one of the fundamental directions in modern quantum materials research. In particular, nodal superconductors are known to appear naturally in strongly correlated systems, including cuprate superconductors and heavy-fermion systems [1][2][3][4][5][6]. Van der Waals materials hosting superconducting states are well known [7-13], yet nodal monolayer van der Waals superconductors have remained elusive [14][15][16][17]. Here, we show that pristine monolayer 1H-TaS2 realizes a nodal superconducting state of f-wave spin-triplet symmetry. We show that including non-magnetic disorder drives the nodal superconducting state to a conventional gapped s-wave state. Furthermore, we observe the emergence of many-body excitations potentially associated to the unconventional pairing mechanism. Our results demonstrate the emergence of nodal superconductivity in a van der Waals monolayer, providing a building block for van der Waals heterostructures exploiting unconventional superconducting states.