Coulomb-engineered heterojunctions and dynamical screening in transition metal dichalcogenide monolayers

Abstract

The manipulation of two-dimensional materials via their dielectric environment offers novel opportunities to control electronic as well as optical properties and allows one to imprint nanostructures in a noninvasive way. Here we asses the potential of monolayer semiconducting transition-metal dichalcogenides (TMDCs) for Coulomb engineering in a material realistic and quantitative manner. We compare the response of different TMDC materials to modifications of their dielectric surrounding, analyze effects of dynamic substrate screening, i.e., frequency dependencies in the dielectric functions, and discuss inherent length scales of Coulombengineered heterojunctions. We find symmetric and rigid-shift-like quasiparticle band-gap modulations for both instantaneous and dynamic substrate screening. From this, we derive short-ranged self-energies for an effective multiscale modeling of Coulomb-engineered heterojunctions composed of a homogeneous monolayer placed on a spatially structured substrate. For these heterojunctions, we show that band-gap modulations on the length scale of a few lattice constants are possible, rendering external limitations of the substrate structuring more important than internal effects. We find that all semiconducting TMDCs are similarly well suited for these external and noninvasive modifications.

Environmental screening and ligand-field effects to magnetism in CrI3 monolayer

“…Finally, our findings render CrI 3 monolayer-based heterostructures with spatially structured environments a possibly fascinating playground to non-invasively structure the magnetic properties of layered magnetic materials similar to what has been discussed for correlation effects in layered semiconductors 20,21,23,47,48 . Together with the recent discovery of other 2D ferromagnets and antiferromagnets we thus expect that magnetic van der Waals heterostructures are the most promising platforms to engineer and design next-generation magnetic and opto-magnetic devices.…”

“…Next to the CrI 3 intrinsic properties, we aim to also understand the role of external screening properties such as resulting for substrate materials or capping dielectrics. To this end, we utilize our WFCE approach 19 , which realistically modifies the CrI 3 Coulomb interaction tensor according to dielectric environmental screening and which has been shown before to reliably describe the environmental screening impact to layered materials 23,48 . In this way we will be able to understand how the electronic band structure and the microscopic magnetic properties are affected, e.g., by encapsulating CrI 3 with hBN or under the influence of bulk substrates.…”

Correlation-induced valley topology in buckled graphene superlattices

“…First, it is important to note that the interaction strengths Ũ and Ṽ depend on the screening created by the substrate of the buckled structure, 50 and as such can be controlled by screening engineering. [50][51][52][53] In the following, we will explore the potential symmetry broken states as a function of the two interaction strengths, keeping in mind that such values would be controlled by substrate engineering. As we change the ratio of the local and non-local interaction, we see that there are two different groundstates, shown in the phase diagram of For Ṽ = 0, this critical value is Ũc ∼ 2t, as expected for honeycomb systems.…”

Controlling magnetic frustration in 1T-TaS$_2$ via Coulomb engineered long-range interactions

“…This is due to the pronounced role of non-local Coulomb interactions, which decisively define many-body properties in low-dimensional systems and which can be simultaneously efficiently externally modified. In this way band gaps [37][38][39][40][41][42][43] as well as excitonic [37,42,44] or plasmonic [45,46] excitations and even topological properties [47] can be precisely tailored in 2D and 1D systems with the help of (structured) dielectric substrates. Furthermore, Coulomb interactions also play a crucial role in magnetic van der Waals materials, affecting the magnetic exchange between localized magnetic moments.…”

“…Third, although we used the 1T-TaS 2 band structure as an example here, the same methodology can be applied to other van der Waals materials such as 1T-NbSe 2 [59,[72][73][74], 1T-NbS 2 [75], 1T-TaSe 2 [76], as well as other 1T-dichalcogenide alloys, and potentially twisted graphene multilayers [77,78], driving them to exotic magnetic phases. As an outlook, Coulomb engineering can also be performed with spatially structured [37,38,41,46,47] or anisotropic [79,80] screening environments giving rise to spatially dependent exchange interactions, that potentially leads to coexisting ground states of different character within the same, homogeneous layered material.…”