Designing Quantum States in Two Dimensional Heterostructures

Vertical heterostructures have emerged as a promising route for designing quantum materials with extraordinary properties. In particular, the interplay between magnetism and superconductivity has garnered significant attention, driven by the potential realisation of topological superconductivity [1]. This research presents notable progress in the synthesis and characterization of two-dimensional materials in ultra-high vacuum environments. By employing scanning tunnelling microscopy (STM) and spectroscopy (STS), along with tight-binding (TB) and density functional theory (DFT) calculations, a comprehensive understanding of these materials has been achieved.<br/><br/>We propose a novel approach utilizing a heterostructure composed of a supramolecular complex (SMC) on a van der Waals (vdW) superconductor. Through our investigations, we demonstrate that the combination of a magnetic SMC with a quasi-2D superconductor, specifically NbSe2, leads to the emergence of Yu-Shiba-Rusinov (YSR) bands—a crucial element for realizing topological superconductivity. The presence of these bands, together with the exotic magnetic ground state of the SMC, is thoroughly examined using scanning tunneling microscopy (STM) and X-ray magnetic circular dichroism (XMCD), complemented by density-functional theory (DFT) calculations. Notably, our approach offers the advantage of employing diverse molecules, atoms, and substrates, enabling highly tunable YSR bands.<br/><br/>Furthermore, we investigate the electronic structure of a ferroelectric 001 SnTe grown on NbSe2. Our DFT calculations reveal a strong binding between Sn and Se atoms within the substrate, resulting in significant modifications to the overall electronic structure and its dependence on the number of atomic layers of SnTe. We also extend the study to SnTe deposited on other vdW layered materials such as TMDs by means of DFT calculations.<br/><br/>Overall, this research contributes to the understanding and advancement of quantum materials, demonstrating the synthesis and characterization of versatile heterostructures and providing insights into their unique properties.<br/><br/>[1] Topological superconductivity in a van der Waals heterostructure. <i>Nature</i> <b>588</b>, 424–428 (2020)