Crystal phases of charged interlayer excitons in van der Waals heterostructures.*

Throughout the years, strongly correlated coherent states of excitons have been the subject of intense theoretical and experimental studies. This topic has recently boomed due to new emerging quantum materials such as van der Waals (vdW) bound monolayers of transition metal dichalcogenides (TMDs). Here, we analyze the collective properties of charged interlayer excitons (CIE) observed recently in bilayer TMD heterostructures[1]. We derive the universal binding energy expressions as functions of the electron-hole effective mass ratio and interlayer separation distance to explain the experimental evidence for the negative CIE to have a greater binding energy than that of the positive CIE[1]. By analyzing these binding energy functions, we predict that new strongly correlated phases — crystal and Wigner crystal — can be selectively realized with TMD bilayers of properly chosen electron-hole effective masses by just varying their interlayer separation distance. Our results open up new avenues for nonlinear coherent control, charge transport and spinoptronics applications with quantum vdW heterostructures. – [1]L.A.Jauregui, et al., Science 366, 870 (2019); [2]I.V.Bondarev, et al, arXiv2002.09988