Steady state valley Zeeman-like splitting in WSe2-MoSe2 heterobilayers via heterostrain-induced pseudomagnetic field

The lifting of valley degeneracy in semiconducting transition metal dichalcogenide heterobilayers is essential for the utilization of interlayer excitons in valleytronic and quantum photonic applications. Previous approaches have relied on external magnetic fields to achieve large valley Zeeman splittings, but these require impractically high field strengths. To efficiently exploit interlayer excitons in valleytronic applications, it is therefore of great importance to further increase this splitting while simultaneously avoiding the use of external magnetic fields. Here, we demonstrate that a heterostrain-induced pseudomagnetic field of $$\approx \,$$ 8T gives rise to a steady-state valley Zeeman-like splitting of nearly 6.5 meV in WSe₂–MoSe₂ heterostructures under linearly polarized excitation. In agreement with theoretical predictions, our measurements show that heterostrain not only generates an effective pseudomagnetic field and the resulting Zeeman-like splitting, but also induces elliptically polarized emission through the breaking of three-fold rotational (C₃) symmetry. The large zero-field splitting observed here under linearly polarized excitation highlights the crucial role of strain in controlling the valley pseudospin. In the future, advanced strain-engineering techniques may enable even larger zero-field Zeeman-like splitting, facilitating the use of valley pseudospin as an information carrier in valleytronic applications without the need for external magnetic fields.