'In both monolayers, there is a special type of superconductivity in which an internal magnetic field protects the superconducting state from external magnetic fields,' Ye explains. Normal superconductivity disappears when a large external magnetic field is applied, but this Ising superconductivity is strongly protected. Even in the strongest static magnetic field in Europe, which has a strength of 37 Tesla, the superconductivity in tungsten disulfide does not show any change. However, although it is great to have such strong protection, the next challenge is to find a way to control this protective effect, by applying an electric field.
Ye and his collaborators studied a double layer of molybdenum disulfide: 'In that configuration, the interaction between the two layers creates new superconducting states.' Ye created a suspended double layer, with an ionic liquid on both sides that can be used to create an electric field across the bilayer. 'In the individual monolayer, such a field will be asymmetric, with positive ions on one side and negative charges induced on the other. However, in the bilayer, we can have the same amount of charge induced at both monolayers, creating a symmetrical system,' Ye explains. The electric field that was thus created could be used to switch superconductivity on and off. This means that a superconducting transistor was created that could be gated through the ionic liquid.