Thermodynamics is one of the founding scientific pillars that has helped us better understand heat engines, biology, ecosystems, and even black holes. While it fundamentally describes large systems... Show moreThermodynamics is one of the founding scientific pillars that has helped us better understand heat engines, biology, ecosystems, and even black holes. While it fundamentally describes large systems by examining the bulk behavior of their constituents, it is anchored in the statistical equivalence of equilibrium configurations of a formally infinite number of microscopic constituents. A question of its validity arises when one scales down to small quantum systems. Here, we have derived dynamic non-equilibrium relations that surprisingly resemble the classical thermodynamics laws, with a mix of quantum features that encode the dynamics of quantum information. Understanding the relation between the out-of-equilibrium dynamics of finite-size quantum systems and their initial thermodynamic state might have been a purely academic exercise fifteen years ago. But now, thanks to ultra-cold atomic quantum simulators and progress in quantum computers, the thermodynamics of finite-size quantum systems has practical implications too. The findings of this thesis contribute to understanding quantum many-body systems, particularly in the context of entanglement, non-equilibrium dynamics, thermalization, and charge transport. Show less
Optical cavities are useful tools to enhance the interaction between light and matter, which is important to make good quantum emitters. However, it turns out that the cavities themselves (without... Show moreOptical cavities are useful tools to enhance the interaction between light and matter, which is important to make good quantum emitters. However, it turns out that the cavities themselves (without any quantum emitters) are already interesting objects to study. When these cavities become very small, non-paraxial effects become important to describe the eigenmodes of the cavity. This thesis describes both the theoretical predictions of the cavity and shows the corresponding experiments. Show less
CrO2, a half-metal ferromagnet, has shown great promise for superconducting spintronics applications for nearly two decades. Josephson junctions consisting of superconducting (S) contacts on... Show moreCrO2, a half-metal ferromagnet, has shown great promise for superconducting spintronics applications for nearly two decades. Josephson junctions consisting of superconducting (S) contacts on ferromagnetic (F) structures of CrO2, have been shown to sustain remarkably high supercurrents over hundreds of nanometers. However, advancements in this area have been hindered by the metastable nature of CrO2 at ambient conditions. This results in a poorly controlled S-F interface transparency, which is critical for generation of spin triplets. This thesis explores the potential, challenges and possible solutions to overcome the issues with CrO2 devices. Show less
Self-assembly offers a promising route to create complex structures and materials using simple building blocks. Through, colloidal self-assembly, we can understand the governing principles of the... Show moreSelf-assembly offers a promising route to create complex structures and materials using simple building blocks. Through, colloidal self-assembly, we can understand the governing principles of the self-assembly process and unlock its potential in diverse applications in materials science, photonics and electronics. The research outlined in this thesis contributes to our understanding of self-assembly processes in binary colloidal systems. It also sheds light on how the shape, size, and number ratio of colloidal particles impact the final structure of colloidal molecules in both electrostatic and DNA-functionalized colloidal assembly, as well as flexible colloidal lattices. This work showcases the potential for creating novel flexible materials with tailored properties. The research findings also provide fundamental insights into the governing mechanism of self-assembly and the route to the development of functional materials and devices with controlled properties and behavior. Show less
In this thesis, we examine various systems through the lens of several numerical methods. We delve into questions concerning thermalization in closed unitary systems, lattice gauge theories, and... Show moreIn this thesis, we examine various systems through the lens of several numerical methods. We delve into questions concerning thermalization in closed unitary systems, lattice gauge theories, and the intriguing properties of deep neural network phase spaces. Leveraging modern advancements in both software and hardware, we scrutinize these systems in greater detail, accessing previously unreachable regimes. Show less
The studies in this thesis are focused on the physical effects in the flat band materials. The results contain the discovery of strong enhancement of RKKY spin-spin interactions with specific... Show moreThe studies in this thesis are focused on the physical effects in the flat band materials. The results contain the discovery of strong enhancement of RKKY spin-spin interactions with specific geometric arrangement and dynamical generation of excitonic order parameter with high magnitude. A number of physical properties influenced by flat band are studied: optical conductivity, orbital susceptibility and spectral functions in the case of flat-band lattices stacked into bilayer. Additional chapters contain the studies of the methods to distinguish Majorana zero modes from Andreev levels and Majorana fermions in superconductors. Show less
In the traditional theory of linear elasticity, superposition dictates that the response of a material does not depend on the sequence of the applied mechanical actuations. In this dissertation, we... Show moreIn the traditional theory of linear elasticity, superposition dictates that the response of a material does not depend on the sequence of the applied mechanical actuations. In this dissertation, we design non-linear building blocks to realize a non-Abelian metamaterial whose response is sequence-sensitive. We study the behaviour of such metamaterials through simulations and experiments using existing mathematical and engineering frameworks such as finite state machines and Boolean logic circuits. We discover that the non-Abelian metamaterial possesses information processing and storage capabilities: it behaves like a simple computer. This opens up new avenues to realize mechanical computing and memory devices with a complex emergent response. Show less
Ferritin is a spherical metalloprotein, capable of storing and releasing iron in a controllable way. It is composed of a protein shell of about 12 nm and within its cavity, iron is stored in a... Show moreFerritin is a spherical metalloprotein, capable of storing and releasing iron in a controllable way. It is composed of a protein shell of about 12 nm and within its cavity, iron is stored in a mineral form. The ferritin core resembles an iron-based nanoparticle that is isolated from the environment by the ferritin shell, which makes ferritin an attractive element to be used in the fabrication of bioelectronic devices. Another intriguing aspect of ferritin is its potential relation to neurodegenerative diseases, such as Alzheimer’s and Parkinson’s. The relation is not yet well understood, but the studies indicate that dysfunctional ferritin appears to play an important role. This dissertation aims to characterize ferritin electrically and magnetically. First, the electrical properties of single ferritin are explored to understand the charge transport through ferritin, and additionally, the first ferritin single-electron transistor is obtained. Second, the magnetic properties of multiple ferritin particles are studied by electron paramagnetic resonance, which supplies information about the ferritin core. A model of the electron-spin structure of the ferritin core is proposed and extended to the ferritin signal from post-mortem brain tissues. Show less
This thesis presents insights from our study of various correlated electron systems with a scanning tunneling microscope (STM). In ordinary metals, electron-electron interactions exist, but get... Show moreThis thesis presents insights from our study of various correlated electron systems with a scanning tunneling microscope (STM). In ordinary metals, electron-electron interactions exist, but get substantially screened due to the sheer number of electrons. We therefore describe electrons in ordinary metals as a gaseous state of free, or weakly interacting charged particles. This adequately explains their properties, however, this picture does not work for correlated electron materials. The prominent electron-electron interactions present in these materials enable a wide range of exotic electronic phenomena, some of which are presented in this work. In chapter 2, we present STM results measured on an overdoped copper oxide compound and show that the superconducting state that occurs in these materials cannot be described by conventional BCS theory, contrary to what is commonly believed. In chapter 3, we study twisted bilayer graphene devices, and quantify their local twist angle and strain on the nanoscale. In chapter 4, we describe how to build and characterize the hardware needed to do noise spectroscopy measurements in a conventional, low temperature STM setup. Finally, in chapter 5, we present our noise spectroscopy measurements on Sr2IrO4, and explain how random telegraph noise could lead to the observed noise enhancements. Show less
The interest of this thesis lies in spin transport in normal metals and superconducting half-metallic junctions. Spin transport is strongly related to the spin polarization (P) of materials. Half... Show moreThe interest of this thesis lies in spin transport in normal metals and superconducting half-metallic junctions. Spin transport is strongly related to the spin polarization (P) of materials. Half-metallic ferromagnets, or half metals, with 100% spin polarization, are of interest as spin injector, promising a high efficiency; but also as a superconducting spin transport channel between two superconducting electrodes, in which spin-poalrized triplets are generated and exist over long distance. Show less
It has been a long-standing mystery how complex biological structures emerge from such seemingly uncoordinated building blocks as cells and tissues, in the presence of only minimal environmental... Show moreIt has been a long-standing mystery how complex biological structures emerge from such seemingly uncoordinated building blocks as cells and tissues, in the presence of only minimal environmental guidance. In particular, unifying descriptions independent of microscopic details of a specific organism are rare. In recent years, hydrodynamics has successfully been applied to describe certain types living systems. The thesis is concerned with understanding different aspects of structure formation in active liquids and biological systems. In the first chapter we investigate the coarsening dynamics in the Toner-Tu theory and compare it with an experimental colloidal system. Afterwards, we investigate the effect of chirality in active nematics, with applications to biological tissues. In the last part we derive and study a model to explain geometric deformations due to the presence of activity. The resulting dynamics might be able to explain morphogenetic processes. Show less
Make more fluid: In condensed matter systems, electrons can acquire unusual properties from their interaction with the atomic lattice. In some examples, they can behave as massless particles,... Show moreMake more fluid: In condensed matter systems, electrons can acquire unusual properties from their interaction with the atomic lattice. In some examples, they can behave as massless particles, mimicking the relativistic behavior of photons. This thesis is dedicated to the study of such massless electronic excitations, focusing on systems exhibiting Majorana, Weyl, and Dirac fermions. In this thesis, we show how new states can arise in the presence of a magnetic field, find new signatures of such states, and present new methods that can be used to study them. Show less
In unconventional high temperature superconductors, supercurrent vortices are known to spoil the Landau levels. In this thesis the emergence of Landau levels is studied in different types of... Show moreIn unconventional high temperature superconductors, supercurrent vortices are known to spoil the Landau levels. In this thesis the emergence of Landau levels is studied in different types of superconductors: Weyl superconductors, and the Fu-Kane heterostructure. It is shown that in those materials the zeroth Landau level can withstand the scattering off vortices. Show less
In this thesis we investigated the ability of two-photon multifocal microscopy for single-molecule microscopy in live cells and organisms. Two-photon excitation combined with multifocal scanning... Show moreIn this thesis we investigated the ability of two-photon multifocal microscopy for single-molecule microscopy in live cells and organisms. Two-photon excitation combined with multifocal scanning has the potential to achieve, high (temporal) resolution imaging at a low background. Splitting the laser beam into multiple beamlets reduced laser power to all but eliminate photobleaching. The low background combined with the fast scan speeds and absence of photobleaching allowed us to measure single-particles and single-molecules in live zebrafish embryo's for long time periods. To the best of our knowledge, it is the first time that single-molecule molecules have been observed in a wide-field two-photon microscope. Show less
Combining ferromagnetism and superconductivity can lead to the development of a completely new generation of technology, with unique and powerful characteristics, called superconducting spintronics... Show moreCombining ferromagnetism and superconductivity can lead to the development of a completely new generation of technology, with unique and powerful characteristics, called superconducting spintronics. The task of developing this, however, is challenging because at the microscopic level the superconducting and ferromagnetic states are intrinsically incompatible. Under certain conditions, however, the conventional (singlet) superconducting state can be converted into the triplet one, with the spins of the electrons forming the Cooper pairs aligned parallel. The triplet state can coexist with ferromagnetism and is very interesting both for applications and from a fundamental point of view. In this thesis we study the electrical properties of small hybrid devices that mainly consist of superconducting and ferromagnetic layers. By measuring the electrical resistance of these devices as a function of parameters such as the temperature or the applied magnetic field, it is possible to indirectly infer important information about the state of the (super)conductivity in the different layers. We investigate different types of devices (multilayers, triplet spin valves and Josephson junctions), in order to address different aspects related to the generation of the triplet state, for a better and better control of the process. Show less
Dissertation. We study the topological properties of strongly externally driven quantum non-interacting quantum systems, focussing on the example of the quantum walk and closely related systems.
A guaranteed source of neutrinos is the production in cosmic ray interactions with the interstellar matter in our Galaxy. The signal has never been detected however and only an upper limit on this... Show moreA guaranteed source of neutrinos is the production in cosmic ray interactions with the interstellar matter in our Galaxy. The signal has never been detected however and only an upper limit on this flux of neutrinos has been published by the AMANDA-II detector. The ANTARES neutrino telescope, located in the Mediterranean Sea, offers a high visibility of the central region of the Milky Way, from where the highest signal is expected. ANTARES data from 2007-2012 were used to compare the flux from a region extending 39 degrees in Galactic longitude and 4.5 degrees in Galactic latitude on either side of the Galactic centre, with the flux from multiple equivalent off-source regions. No significant excess has been observed, and upper limits have been placed on the neutrino flux. The flux limits produced with ANTARES are more than a factor of 10 above the model predictions, which means that a bigger neutrino telescope is needed to constrain the models further. The future KM3NeT telescope is well suited to perform this measurement. Simulations show that by using all neutrinos flavours, KM3NeT should be able to seriously constrain the neutrino flux after about 3 years of operation. Show less
The work described in this thesis was aimed at the study of the functional properties of (isolated and purified) biomolecular systems at the single-molecule level. Two prerequisites are essential... Show moreThe work described in this thesis was aimed at the study of the functional properties of (isolated and purified) biomolecular systems at the single-molecule level. Two prerequisites are essential for successfully achieving this goal. First of all, single biomolecules should be observable, which means that they should be natively fluorescent or they should be rendered fluorescent by suitable biochemical or biomolecular 12 engineering. The other challenge is to engineer the system in such a way that the fluorescence intensity reports the actual, functional state of the biomolecule. Show less
Charge counting statistics (C.S.) of traversing electron in quantum devices like atomic-molecular junctions is sensitive to the local perturbation in the charge field at the contact and in the... Show moreCharge counting statistics (C.S.) of traversing electron in quantum devices like atomic-molecular junctions is sensitive to the local perturbation in the charge field at the contact and in the quantum channels. The first cumulant of C.S. i.e. current-voltage characteristic of such devices has been tool for such investigation since long time. Here we have used the second cumulant i.e. shot noise to study the electron-electron and electron-phonon interaction in the atomic contacts. The shot noise measurement on the Au atomic chain reveals the inelastic scattering in the noise. These signatures can provide vital information on the feedback of the local phonon population on electron transport. The current-voltage characteristic of the ferromagnetic atomic contacts unexpectedly shows zero bias anomalies. This observation is attributed to the interaction of traversing electron with localized magnetic moments within same host species. The observed connection between the Fano factor and the weight of the zero bias anomalies supports the view that the zero bias anomaly originates from spin scattering by localized magnetic moments. However, whether this is true Kondo scattering as suggested by Calvo et al. cannot be stated conclusively from our data. At the end of thesis we have presented a low noise high frequency broadband noise measurement setup suitable for break junction setup. Show less
