Description
Mechanical strain offers a powerful means of manipulating a material's symmetries. Here, we demonstrate an approach to induce mechanical strain with controlled tensorial components in 2D materials and heterostructures at cryogenic temperatures. We use this technique to investigate the many-body behaviors of excitons. First, we show that normally “dark” excitons with vanishing oscillator strength can be accessed and studied in strained devices. Second, we establish the valley character of intervalley excitons by analyzing their distinct strain signatures. Finally, we demonstrate that uniaxial strain manipulates the valley degree of freedom analogously to a spin in a magnetic field. We use this insight to establish the many-body character of debated excitonic states.
