This work is dedicated to electron transport in atomically thin crystals. We explore hydrodynamic effects in the electron liquid of graphene and perform a comprehensive study of electronic and optical properties of a novel 2D semiconductor - indium selenide(InSe). Graphene hosts a high quality electron system with weak phonon coupling such that electron-electron scattering can be the dominant process responsible for the establishment of local equilibrium of the electronic system above liquid nitrogen temperatures. Under these conditions, charge carriers are expected to behave as a viscous fluid with a hydrodynamic behaviour similar to classical gases or liquids. In this thesis, we aimed to reveal this hydrodynamic behaviour of the electron fluid by studying transport properties of high-quality graphene devices. To amplify the hydrodynamic effects, we used a special measurement geometry in which the current was injected into the graphene channel and the voltage was measured at the contact nearest to the injector. In this geometry we detected a negative signal which is developed as a result of the viscous drag between adjacent fluid layers, accompanied by the formation of current vortices. The magnitude of the signal allowed us to perform the first measurement of electron viscosity. In order to understand how an electron liquid enters the hydrodynamic regime we studied electron transport in graphene point contacts. We observed a drop in the point contact resistance upon increasing temperature. This drop was attributed to the interaction-induced lubrication of the point contact boundaries that was found to be strong enough to prevent momentum relaxation of charge carriers. The viscosity of the electron fluid was measured over a wide range of temperatures and at different carrier densities. Experimental data was found to be in good agreement with many-body calculations. In this work we also studied transport properties of two-dimensional InSe. We observed high electron mobility transport, quantum oscillations and a fully developed quantum Hall effect. In optical studies, we revealed that due to the crystal symmetry a monolayer InSe features suppressed recombination of electron-hole pairs.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:728021 |
| Date | January 2017 |
| Creators | Bandurin, Denis |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/electron-transport-in-atomically-thin-crystals(e184d9d8-ad44-41e0-8be9-bd381d6a21d6).html |
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