Nonreciprocal transport properties of solid state quantum devices

Abstract

Electronic devices are used for a broad range of applications in our everyday lives. Most of these devices are well described by semiclassical physics. Some devices, however, can only be modeled if quantum mechanical effects, such as quantum tunneling or superconductivity, are taken into account. Interestingly, classical and quantum physics do not always harmonize well when designing electronic devices. For classical electronic devices, quantum effects are usually undesired, as they may lead to detrimental behavior for small device sizes. For quantum electronics, the classical behavior such as scattering events that cause dissipation is unwanted, because it leads, for example, to a reduction of the quantum coherence times of qubits. Thus, in the development of quantum and classical electronics, it is natural to avoid the respective other realm as far as possible. Indeed, the transition regime between quantum and classical physics has not received much attention as an asset for device development. Given this situation, this thesis presents a theoretical and experimental exploration of novel electronic devices that combine the quantum mechanical and classical properties of the electron system. These devices achieve properties that are impossible to achieve if only classical or only quantum mechanical dynamics are considered. The theoretical part of this thesis analyzes how electronic transport properties are affected if the unitary time evolution of isolated quantum systems is replaced with a nonunitary time evolution of a quantum system that is coupled to a classical environment. The experimental part discusses the fabrication and transport measurements of corresponding mesoscopic electronic devices at low temperatures.