Van der Waals heterostructures present unique opportunities to synthesise quantum materials. For example, atomically-thin transition metal dichalcogenides (TMDs) possess three quantum degrees of freedom: real spin, valley pseudospin, and layer pseudospin. TMD heterobilayers, in which electrons and holes reside in separate layers to form long-lived interlayer excitons (IX), offer superlative access to these features. Further, the relative stacking angle of TMD heterobilayers creates a moir’e superlattice which modulates the electronic band structure in a tunable yet precise way, leading to spatial confinement of single particle wavepackets. Here we report the observation of spin-layer locking of interlayer valley excitons trapped in moir’e potentials. In a heterostructure of bilayer 2H-MoSe$_2$ and monolayer WSe$_2$, the phenomenon of locked electron spin and layer pseudospin leads to two quantum-confined IX species with distinct spin-layer-valley configurations. Furthermore, we observe the 2H-MoSe$_2$ intrinsically locks the atomic registries of the trapped IX species together. These results identify the layer pseudospin as a useful degree of freedom to engineer highly-tunable few-level quantum systems in two-dimensional heterostructures.

Published : "arXiv Mesoscale and Nanoscale Physics".