Supervisor: Renato Gonnelli
The electric field effect is the modulation of the transport properties of a material obtained through the application of a strong electric (electrostatic) field at its surface. It is widely applied in semiconductors (typically in the well-known field-effect transistors), and its usage has been extended to graphene and other two-dimensional materials after their discovery.
The introduction of an innovative technique for the generation of the electric field (exploiting the formation of a nanoscale capacitor at the interface between a solid-state material and an electrolyte) allows one to reach extremely intense electric fields, not only inducing changes in the resistance but full-blown phase transitions in the materials under study.
An egregious example is the transformation of two-dimensional semiconductor molybdenum disulphide first into a metal and then into a superconductor at the increase of the applied electric field. Such results have received a lot of attention by the scientific community due to their relevance for nanoscience and nanotechnology.
The group has a long experience in this field, and has achieved relevant results on various 2D or layered materials like few-layer graphene, MoS2, iron-based superconductors, but also on normal metals (Au, Ag, Cu) and conventional superconductors (NbN). Collaborations on this topic are established with:
- Cambridge Graphene Centre, Cambridge University (UK)
- Zernike Institute for Advanced Materials (ZIAM), University of Groningen (The Netherlands)
- National Institute for Metrological Research, INRiM (Torino)
- Nagoya University (Japan)
- MIT - Massachusetts Institute of Technology, Cambridge, (USA)
The thesis here proposed envisages a mainly experimental work, which includes:
- participation to the fabrication of field-effect devices (material exfoliation, optical/electronic lithography, contact deposition)
- electric transport measurements (resistivity, magnetoresistance, Hall effect) as a function of the electric field, temperature (0.3 K – 350 K) and the magnetic field (up to 9 Tesla)
- data analysis, including the development or the generalization of models for data fitting
- interpretation of the results in light of the existing theories and the established literature.
Selected References
Daghero et al., Phys. Rev. Lett. 108, 066807 (2012)
Gonnelli et al., 2D Mater. 4, 035006 (2017)
Piatti et al., Phys. Rev. B 95, 140501 (R) (2017)
Piatti et al., Nano Lett., 18, 4821 (2018)