Graphene
I am currently working on the study of hybrid systems graphene-semiconductor.
They can represent the future
for the realization of coherent circuits with minimal dissipation and nanodevices including analog-to-digital
converters and topologically protected quantum bits. In the following, I introduce the topic I have been experimentally involved in.
Transport properties of graphene need a deep understanding and extensive investigations with the aim of assessing the real potential of this novel material for future nanoelectronics. Furthermore, fundamental studies of electron-electron interaction effects in two spatial dimensions can be carried on in experimentally feasible systems.
Our studies in this area of research are centered on quantum transport in graphene-based double-layer nanostructures (see figure below). The typical system is represented by a novel hybrid vertical heterostructure for transport studies of inter-layer excitons, which is comprised of an exfoliated graphene sheet deposited on the surface of a GaAs quantum-well heterostructure hosting a shallow 2-dimensional electron gas.
The architecture of the devices we have constructed (see figure below) presents several advantages over GaAs 2DEG-2DEG and graphene-graphene bilayer systems.
- it is much easier to fabricate in comparison with all-semiconductor electron-hole double quantum wells;
- in the structure we propose, measurements of voltage drops at low temperatures are not hampered by mesoscopic fluctuations
Our double-layer Dirac-Schroedinger hybrid electron system is studied for its capability to display interesting correlated states (and associated transport anomalies) induced by interlayer interactions deep in the quantum Hall regime.
(click to enlarge)
Coulomb-drag transport measurements are currently under investigation and can open to new insights on the effects of electron-massless dirac Fermion interaction. The electronic fluids in the two subsystems, the graphene sheet and GaAs quantum well, are independently contacted, so that they electrically isolated. Inter-layer tunnelling is found to be negligible due to the thick Al-GaAs barrier in between. Electrons roaming in the GaAs quantum well are therefore coupled to graphene carriers and viceversa only by virtue of Coulomb interactions, which are long-range in nature.
Part of the work in this area of research has been done in collaboration with A.C. Ferrari (University of Cambridge, UK) and F. Koppens (ICFO, Spain).
