Systematics of molecular self-assembled networks at topological insulators surfaces

TL;DR

This paper demonstrates that molecular self-assembly can create well-defined, tunable nanoscale networks on topological insulator surfaces, improving interface control and enabling tailored electronic and magnetic properties.

Contribution

It introduces a method to precisely control topological insulator interfaces using molecular self-assembly and chemical modifications, enhancing device potential.

Findings

Molecular self-assembly forms ordered networks on TI surfaces.

Chemical modifications control the symmetry of molecular overlayers.

Charge redistribution at the interface influences electronic properties.

Abstract

The success of topological insulators (TI) in creating devices with unique functionalities is directly connected to the ability of coupling their helical spin states to well defined perturbations. However, up to now, TI-based heterostructures always resulted in very disordered interfaces, characterized by strong mesoscopic fluctuations of the chemical potential which make the spin-momentum locking ill-defined over length scales of few nanometers or even completely destroy topological states. These limitations call for the ability to control topological interfaces with atomic precision. Here, we demonstrate that molecular self-assembly processes driven by inherent interactions among the constituents offer the opportunity to create well-defined networks at TIs surfaces. Even more remarkably, we show that the symmetry of the overlayer can be finely controlled by appropriate chemical modifications. By analyzing the influence of the molecules on the TI electronic properties, we rationalize our results in terms of the charge redistribution taking place at the interface. Overall, our approach offers a precise and fast way to produce tailor-made nanoscale surface landscapes. In particular, our findings make organic materials ideal TIs counterparts, since they offer the possibility to chemically tune both electronic and magnetic properties within the same family of molecules, thereby bringing us a significant step closer towards an application of this fascinating class of materials.