We investigate how radiation pressure can be used to influence the mechanical motion of a micro-mirror suspended from springs. This trampoline resonator is part of an optical Fabry-Perot cavity. By... Show moreWe investigate how radiation pressure can be used to influence the mechanical motion of a micro-mirror suspended from springs. This trampoline resonator is part of an optical Fabry-Perot cavity. By tuning the laser frequency with respect to the optical resonance, we are able to optically cool the mechanical motion of the resonator. When combining this optical cooling with cryogenic cooling techniques, we are able to bring the mechanical resonator close to the quantum mechanical ground state. This is a requirement for future experiments to investigate the fundamentals of quantum mechanics. Show less
This thesis is devoted to the effects of disorder on two-dimensional systems of Dirac fermions. Disorder localizes the usual electron system governed by the Schroedinger equation. The influence of... Show moreThis thesis is devoted to the effects of disorder on two-dimensional systems of Dirac fermions. Disorder localizes the usual electron system governed by the Schroedinger equation. The influence of disorder on Dirac fermions is qualitevely different. We concentrate on a random mass term in the Dirac equation. We have discovered that Dirac fermions in graphene are localized by a random mass, without any transition into metallic state. The situation is entirely different for Dirac fermions in a p-wave superconductor. There electrostatic disorder appears in the Dirac equation as a random mass, which localizes the excitation, but only if the disorder is relatively weak. For large mass fluctuations a transition into metallic state appears. This qualitatively different response to disorder in graphene and in p-wave superconductors is explained by the appearance of Majorana bound states, which allow for resonant tunneling and metallic state. Electrostatic disorder in a d-wave superconductor represented as random vector potential in the Dirac equation. We look at the transmission of Dirac fermions for electrostatic potential with long- and short-range fluctuations. We study the interplay of electrical and mechanical properties of suspended graphene by calculating the correction to the conductivity due to its deformation by a gate electrode. Show less
