Transition metal dichalcogenides have a similar structure to graphene yet have a wide variety of different electrical properties ranging from semiconducting to superconducting or charge density waves. These phases are determined by the particular atoms in the structure, the number of layers and the temperature.

Using Fourier transform scanning tunneling spectroscopy, we have mapped the band structure in one of these TMDs, tungsten diselenide. We have found that in monolayer WSe2, there is a large spin splitting at the top of the valence band which forbids scattering from the K to K' valleys. Similarly, in bilayer WSe2 we have also observed spin-valley-layer coupling in the conduction band near the Q point. This work has been published in Physical Review Letters.