Electric field tunable superconductor-semiconductor coupling in Majorana nanowires

We study the effect of external electric fields on superconductor-semiconductor coupling by measuring the electron transport in InSb semiconductor nanowires coupled to an epitaxially grown Al superconductor. We find that the gate voltage induced electric fields can greatly modify the coupling strength, which has consequences for the proximity...

Electrodynamics of strongly disordered superconductors

Thin films of superconducting materials with a high resistance in the normal state, such as TiN, NbTiN, NbN and InO, are intensively studied from both an application and a fundamental point of view. A spatially inhomogeneous superconducting state can arise in these materials as a result of the strong disorder. This Thesis provides an...

Quasiparticle dynamics in aluminium superconducting microwave resonators

This thesis describes the intrinsic limits of superconducting microresonator detectors. In a superconductor at low temperature, most of the electrons are paired into so called Cooper pairs, which cause the well-known electrical conduction without resistance. Superconducting microwave resonators have therefore very high quality factors and are...

Improved Nb SIS devices for heterodyne mixers between 700?GHz and 1.3?THz with NbTiN transmission lines using a normal metal energy relaxation layer

In this paper, we demonstrate experimentally the implementation of a niobium-trilayer junction with an aluminum-oxide tunnel barrier, embedded in a high-gap superconducting niobium-titanium-nitride circuit. Previously reported heating by quasiparticle trapping is removed by inserting a normal metal layer of gold between the niobium junction and...

Non-equilibrium electron transport in mesoscale superconducting hybrids

This thesis focusses on driven superconducting heterostructures. Both experimentally and theoretically we address the following questions: (a) how does the presence of different metallic and dielectric materials influence the electronic properties of a driven superconductor? (b) how does a non-equilibrium electron distribution arise and how does...

Photon-detecting superconducting resonators

One of the greatest challenges in astronomy is observing star and planetary formation, redshifted distant galaxies and molecular spectral ‘fingerprints’ in the far-infrared spectrum of light, using highly sensitive and large cameras. In this thesis we investigate superconducting resonators for photon detection. In superconductors the electrons...

Tuning the charge density wave and superconductivity in CuxTaS2

We report the characterization of layered 2H-type CuxTaS2 for 0?x?0.12. The charge density wave (CDW), at 70 K for TaS2, is destabilized with Cu doping. The sub-1 K superconducting transition in undoped 2H-TaS2 jumps quickly to 2.5 K at low x, increases to 4.5 K at the optimal composition Cu0.04TaS2, and then decreases at higher x. The...

Singlet and triplet supercurrents in disordered mesoscopic systems

This thesis describes a series of experiments and a theoretical study in order to understand and control the behavior of electrons in many-body systems. In particular, the experiments concentrate on competition between the - antagonistic - electronic states of superconductivity and ferromagnetism, and are strongly motivated by the recent...

Magnetic Properties of Uranium Based Ferromagnetic Superconductors

Ferromagnetism and superconductivity have long been thought to be mutually exclusive. Recently however it was found that the compounds UGe2, URhGe and UIr belong to a class of materials in which ferromagnetisme and superconductivity appear simultaneously. One characteristic property of these compounds is the existence of strong correlations...

Quantum transport in molecular devices and graphene

As a result of progress in nanotechnology, smaller and smaller electronic circuits can be made. The stage of electrically contacting even a single molecule has now been reached. This stimulates both fundamental and applied research alike. Molecular electronics is hence a booming new field that draws a lot of attention. In this research project...

Quantum transport in semiconductor nanowires

This thesis describes a series of experiments aimed at understanding the low-temperature electrical transport properties of semiconductor nanowires. The semiconductor nanowires (1-100 nm in diameter) are grown from nanoscale gold particles via a chemical process called vapor-liquid-solid (VLS) growth. The huge versatility of this material system...

Coherent Transport in Superconducting and Ferromagnetic Hybrid Systems