Researchers from the University at Buffalo discovered a new way to split the energy levels between the valleys in a two-dimensional semiconductor. The researchers used a ferromagnetic compound to pull the valleys apart and keep them at different energy levels - which enables an increase in the separation of the energy in the valley by a factor of 10 compared to an external magnetic field.

Valley energy seperation on WSe2 over EuS (U of Buffalo)

The whole device is a two-layered hterostructure made from a 10-nm thick film of europoium sulfide (EuS) which is magnetic and a single layer (<1nm) layer of tungsten diselenide (WSe2) on top. The magnetic field of the bottom layer forced the energy separation of the valleys in the WSe2.