Proximity Control of Single Photon Emitting Heterointerfaces

Heterointerfaces of two-dimensional materials are an ideal design space for advanced quantum devices due to the simplicity of stacking different layers to combine their electronic properties. Valleytronic devices are a rapidly emerging example of this principle in application. Materials with inherent time-reversal symmetry, such as transition metal dichalcogenides, can have two equivalent electron valley states in momentum space. Applying a magnetic field breaks the symmetry between these states, unlocking the ability to selectively emit or absorb polarized light at different wavelengths, with many applications in information processing and quantum communication. Valley symmetry can also be broken by stacking the valleytronic material on a two-dimensional magnetic layer, with the proximity-induced valley splitting potentially much stronger than can be achieved with practical external field strengths. The interlayer exchange interaction is strongly dependent on the degree of orbital hybridization between the two materials, which in turn is influenced by the relative energy alignment of their band edges. Experimentally, this has been adjusted by placing the materials under a strain gradient, which not only tunes the exchange interaction but also creates local extrema in the bands and traps excitons into a highly localized state that emits individual photons.<br/>This talk will discuss our latest results on a selected set of chalcogenide heterointerfaces. In particular, we will present our density functional theory computational screening results on a wide range of heterointerfaces with a potential for valley splitting. In addition to presenting our findings in terms of the most promising systems, the associated pitfalls and challenges in the computations will be also be highlighted. We will close by addressing the interplay of strain, defects and band alignment in these complex two-dimensional material systems that can lead to single photon emission, as observed in several recent experiments for transition metal dichalcognide/two-dimensional ferromagnet heterointerfaces.