Electric field control of topological Weyl semimetals

Weyl semimetals are a recently discovered class of materials that present unique topological properties. In the last years, they have been a topic of great interest for research, but few applications have been proposed to exploit their unique characteristics. The transport properties of Weyl semimetals make them very promising for applications in electronics, especially at low temperatures. This work is focused on the interaction of these materials with an electric field, with the aim to study the behavior of gated devices with a Weyl semimetal channel. The first model studied was the one of a Klein tunneling transistor, a device where the effect of the gate is to shift the energy bands of a portion of the channel, creating an energy barrier that reflects some of the incoming carriers. This model was improved by adding the screening effect of the potential applied by the gate electrode inside the material, and showing that this effect is playing an important role in the modulation of the current passing through the device. The next step was studying more in detail the screening effect in Weyl semimetals, to improve the accuracy of the previous model, as well as future models of field-effect devices. A screening model was developed, taking into account the contribution of both the bulk and surface states of the material. This model provides information on the potential decay as we move deeper into the material, and on the excess charges that are accumulated inside it. Finally, the fabrication process that leads to the realization of test devices is explained. The measurements obtained from these devices will be a way to test the results of the presented models, providing insights on the properties of the materials and on the next steps needed to realize transistors with good performances.