Abstract: Novel quantum phases of matter and developing practical control over their characteristics is one of the primary aims of current condensed matter physics. It offers the potential for a new generation of energy, electronic and photonic technologies. Among all the newly found phases of matter, topological insulators are novel phases of quantum matter with fascinating bulk band topology and surface states protected by specific symmetries. For example, at the boundary of a strong topological insulator and a trivial insulator, metallic surface states appear that are protected by time-reversal symmetry. As a result, the bulk continues to be insulating, while the surface can support exotic high-mobility spin-polarized electronic states. Since there is no such thing as a clean system, impurities and other disorders are always present in materials. Even while impurities appear to be unfavorable to a system at first look, doping the host system with impurities allows us to engineer different electronic properties of systems, such as the Fermi level or electron density. Because of the symmetry protected metallic states in topological insulators, charge transport responds distinctively to magnetic and non-magnetic impurities. This doctoral dissertation explores how the longitudinal charge transport in magnetic topological thin films and the anomalous Hall effect on the surface of 3D magnetic topological insulators is influenced by point-like and randomly distributed dilute magnetic impurities. We are interested in how charge transport in these systems responds to the orientation of the magnetization orientation and how this response evolves based on the system's main characteristics, such as the magnitude of the Fermi level or gate voltage. Because topological insulators have a strong spin-orbit coupling, the interaction between conducting electrons and local magnetic impurities is very anisotropic. We will show that this anisotropy even enhances when magnetic topological thin films are exposed to a substrate or gate voltage. Therefore, to properly capture this anisotropy in charge transport calculations, we rely on a generalized Boltzmann formalism together with a modified relaxation time scheme. We show that magnetic impurities affect the charge transport in topological insulators by inducing a transition selection rule that governs scatterings of electrons between various electronic states. We see that this selection rule is highly sensitive to the spin direction of the magnetic impurities as well as the position of the Fermi level. According to this selection rule and depending on the position of the Fermi level, two different transport regimes are realized in magnetic topological thin films. In one of these regimes, our findings show that a dissipation less charge current can be generated. In other words, even if there are many magnetic impurities in the system, electrons do not notice them and, remarkably, conduct charge without dissipation. Outside this regime, the charge transport is always dissipative and its sensitivity to the spatial orientation of the magnetic impurities can be effectively modulated by a substrate or gate voltage. In this doctoral thesis, we also explore the anomalous Hall effect (AHE) on the surface of 3D magnetic topological insulators. The AHE is generated by three mechanisms: the intrinsic effect (owing to a nonzero Berry curvature), the side jump effect, and the skew scattering effect. They compete to dominate the AHE in distinct regimes. Analytically, we calculate the contributions of all three mechanisms to the scattering of massive Dirac fermions by magnetic impurities. Our results reveal three transport regimes based on the relative importance of the engaged mechanisms. The identification of these three distinctive transport regimes can assist experimentalists in achieving a regime in which each contribution is dominant over the others, allowing them to measure them separately. Typically, this is not feasible empirically since the total value of the experimentally observed AHE conceals the specific information of each of the three contributions. Based on our analytical calculations, we prove that the AHE can change sign by varying the orientation of the surface magnetization, the concentration of impurities, and the location of the Fermi level, which is consistent with previous experimental findings. In addition, we show that by suitably adjusting the given parameters, any contribution to the AHE, or even the entire AHE, can be turned off. For example, in a system with in-plane magnetization, one can turn off the AHE by pushing the system into the completely metallic regime. Furthermore, we demonstrate that any contribution to the AHE, or even the whole AHE, can be turned off by appropriately changing the provided parameters. For example, in a system with in-plane magnetization, the AHE can be turned off by pushing the system into the fully metallic regime.

Abstract: The precise control of skyrmionics and magnonics in magnetic materials is key to the development of novel spin-based technology and information transport applications. Essentially, the inherent stability of magnetic skyrmions (provided by their topological charge) together with their extremely small size (down to a few nanometers) and the ultralow threshold current necessary to move them in nanostructures are the main advantages of skyrmionics. Not least, magnonics offers lower power consumption compared to electronics and the excitation of high frequency (sub-100~nm wavelength) magnons makes it possible for the creation of nanometric devices for ultrafast information transport. Even though extensive research has been carried out in recent years, the precise manipulation of skyrmions and spin waves (magnons) in nanostructures is not fully mastered and needs to be addressed before making functional skyrmionic and magnonic devices. In this thesis, we reveal multiple alternatives for the manipulation of skyrmions and spin-waves in different materials, such as bulk chiral magnets, heterochiral structures, magnet-supperconductor hybrids and two-dimentional magnetic materials. We make use of a multiscale model to numerically simulate the magnetic states at each considered material, from micromagnetic to atomistic control. We first explore the different nucleation mechanisms, activation energy, and the time evolution of the skyrmion formation in chiral magnetic films, crucial for the realization of skyrmion-based devices. We show that the skyrmion lattice is formed from the conical phase progressively, most probably by the formation of chiral bobbres, followed by the cylindrical growth of individual skyrmions from the film surface. That reflects a rod-like (one-dimensional) nucleation of the skyrmion phase, with an activation barrier of several electronvolts per skyrmion for the case of MnSi (Manganese monosilicide). In addition, we reveal the interesting blinking (creation-annihilation) behavior of skyrmions close to the phase boundary between the conical and skyrmion phases, where we recall that such switching between topologically distinct states has been proposed as a bit operation for information storage. Next, we discuss the motion of ferromagnetic and antiferromagnetic skyrmions in heterochiral magnets. We report the characteristic deflection of ferromagnetic skyrmions when moving across a heterochiral interface, where the extent of such deflection is tuned by the applied spin-polarized current and the magnitude of Dzyaloshinskii-Moriya interaction. Following, we show that the antiferromagnetic skyrmion achieves much higher velocities than its ferromagnetic counterpart, yet experiences far stronger confinement in nanoengineered heterochiral tracks, which reinforces antiferromagnetic skyrmions as a favorable choice for skyrmion-based devices. After that, we study the interesting coupling of magnetic skyrmions and superconducting vortices in magnet-superconductor heterostructures. We perform numerical simulations, based on experimental observations, to demonstrate that the stray field of magnetic skyrmions can nucleate antivortices in an adjacent superconducting film, giving rise to a hybrid topological object, the skyrmion-vortex pair, which harbor promising features for skyrmionics and quantum computing applications. We then explore the manipulation of a single skyrmion-vortex pair when currents are applied into both superconducting and magnetic parts of the heterostructure, which is of importance for the facilitated skyrmion guidance in racetrack applications. Afterwards, we make use of the high tunability of magnetic parameters in two-dimensional magnetic materials to reveal the rich phase diagram of exotic magnetic configurations in magnetic monolayers with suppressed nearest-neighbour exchange, where we show that several unique cycloidal, checkerboard, row-wise and spin-ice states are stabilized by the competition between the second-nearest-neighbor exchange, Dzyaloshinskii-Moriya, and dipolar interactions. Additionally, we show the coexistence of ferromagnetic and antiferromagnetic spin-cycloids, as well as novel types of skyrmions and chiral domain walls. Finally, in the last part of the thesis, we present the spin wave properties in the two-dimensional magnetic materials CrBr$3$ and CrI$3$. Using spin-dynamics simulations parametrized from first principles, we reveal that the spin wave dispersion in such materials can be tuned in a broad range of frequencies by strain-engineering, and that a designed pattern of strain, as well as structural defects (halide vacancies) can be turned useful in the design of spin-wave guides. Lastly, we discuss the realization of magnonic crystals by moiré-periodic modulation of magnetic parameters in van der Waals heterostructures, where we show that the several nanometer small periodicities in such samples are ideal for the interference of terahertz spin waves. Recalling the wide range of possibilities for manipulating spin waves in such two-dimensional materials, we therefore suggest these systems as a front-runner for prospective terahertz magnonic applications.

Abstract: The pursuit for the next generation of nanodevices made scientists focus the attention to two dimensional materials. Experimental works of two dimensional materials are hardly free of structural defects, which, in turn, modify drastically the physical properties of its defect-free counterpart. In this work the presence of structural defects is study in two different materials. First, the dependence of the Hall, bend and longitudinal resistances to a perpendicular magnetic field and to vacancy defects in a four-terminal phosphorene single layer Hall bar is investigated. A tight-binding model in combination with the Landauer-Büttiker formalism is used to calculate the energy spectrum, the lead-to-lead transmissions, and the Hall and bend resistances of the system. It is shown that the terminals with zigzag edge orientation are responsible for the absence of quantized plateaus in the Hall resistance and peaks in the longitudinal resistance. A negative bend resistance in the ballistic regime is found due to the presence of high- and low- energy transport modes in the armchair and zigzag terminals, respectively. The system density of states, with single vacancy defects, shows that the presence of in-gap states is proportional to the number of vacancies. Quantized plateaus in the Hall resistance are only formed in a sufficiently clean system. The effects of different kinds of vacancies in the regime where the quantized plateaus are destroyed and a diffusive regime appears in the bend resistance are investigated. Next, we explore effects due to point defect clustering on the electronic and transport properties of bilayer graphene nanoribbons, for AA and AB stacking and zigzag and armchair boundaries, by means of the tight-binding approach and scattering matrix formalism. Evidence of vacancy concentration signatures exhibiting a maximum amplitude and an universality regardless of the system size, stacking and boundary types, in the density of states around the zero-energy level are observed. Our results are explained via the coalescence analysis of the strong sizeable vacancy clustering effect in the system and the breaking of inversion symmetry at high vacancy densities, demonstrating a similar density of states for two equivalent degrees of concentration disorder, below and above the maximum value.

Abstract: This piece of work is twofold. First, the time evolution of wave-packets in 2D systems is analyzed by the Split-Operator technique in three different scenarios: in multilayer phosphorene, the transient oscillations in the time-dependent average of position and momentum were observed due to the zitterbewegung effect, and the wave packet propagates non-uniformly along the space deforming itself into an elliptical shape. These results were corroborated by the Green’s function formalism except for large values of the wave-vector and long times; in 2D semiconductor quantum wires (QWs) with anisotropic effective masses and different angle orientations with respect to the anisotropic axis. We have shown that the greater this angle, the smaller is the energy levels spacing implying in an increase of the accessible electronic states. Additionally, for non-null magnetic field, the quantum Hall edge states are significantly affected by the edge orientation. In the anisotropic case damped oscillations in the average values of velocity in both x and y directions where obtained. Theses oscillations are originated by the QW geometry but also from subwavepackets with different momentum orientations, whereas for isotropic QWs the wavepacket disperses without splitting; in the third scenario the split-operator technique was used to study the Landau levels, the wave packet trajectories and velocities of electrons in graphene at low-energy regime described by a modified Dirac equation where the momentum-operator is written in a generalized form as result of applying the position-dependent translation operator formalism (PDTO). In the second part of this thesis, the electronic and tunneling properties of α − T3 lattices were studied. Electrons in these lattices behave analogous to integer-spin Dirac Fermions. The presence of a third atomic site in the unit cell leads to a flat band in the energy spectrum, providing unique electronic and tunneling properties. The presence of a super-periodic potential and the inclusion of symmetry-breaking terms results in deviations of the atomic equivalence between the atomic sites affecting the Dirac points and the band-gap. Small deviations in the equivalence between the atomic sites and the number of barriers change the transmission properties in these lattices. Additionally, new tunneling regions are possible by adjusting the symmetry between the atomic sites and affect the omnidirectional total transmission called super-Klein tunneling observed in these lattices. We compare those results to the tunneling probabilities through regions where the energy spectrum changes from linear with a middle flat band to a hyperbolic dispersion.

Abstract: Superconductivity is one of the most important discoveries of the last century. With many applications in physics, engineering, and technology, superconductors are crucial to our way of living. Several material and engineering issues however prevent their widespread usage in everyday life. Comprehensive studies are being directed at these materials and their properties to come up with new technologies that will address these challenges and enhance their superconductive capabilities. In this context, numerical modeling plays an important role in the search of new solutions to existing material and engineering issues. The time-dependent Ginzburg-Landau (TDGL) theory is a powerful predictive tool for modeling the macroscopic behavior of superconductors. However most of the numerical algorithms developed so far are incapable of describing many basic properties of real superconducting devices, and are too slow on current hardware for large-scale numerical simulations necessary for their accurate description. Therefore, the purpose of this thesis is to develop high-performing numerical solutions that can correctly describe material features to be used as modeling tools of laboratory experiments. Some important innovations introduced in this work include the numerical modeling of nonrectangular geometrical shapes with complex electrical and insulating components, the inclusion of dynamic heating of the material, and the description of different types of material inhomogeneities. These encompass the principal features necessary for a complete description of the superconductive physics in real material samples. In this thesis a numerical solution is developed for modeling superconducting thin films and used to study the superconductive properties of three experimental configurations: the dynamics of vortex matter in a Corbino disk, the motion of ultrafast vortices in an hourglass-shaped microbridge, and the photon detection process in a meander-patterned nanowire. Moreover, a numerical solution is developed for modeling three-dimensional superconductors which are studied here for the first time in the type-I superconducting regime. These numerical algorithms are optimized to exploit the computational horsepower of graphics processing units (GPUs) and multicore central-processing unit (CPU) clusters such that they can achieve high-performance and be used to model large-scale problems previously impossible on conventional machines. Several computational tools are also designed to assist with the modeling of superconducting devices. These include a numerical library of the TDGL equations, a novel mechanism for the generation of complex geometries, a closed-form solver to conduct numerical simulations, and a graphics user interface (GUI) to visualize the dynamic behavior of superconductors. The contributions in this thesis ultimately push the boundaries on what is possible in state-of-the-art numerical modeling of superconductivity.

Abstract: abstract not available

Abstract: Polarons are quasiparticles emerging in materials from the interaction of extra charge carriers with the surrounding atomic lattice. They appear in a wide va- riety of compounds and can have a profound impact on their properties, making the concept of a polaron a central and ubiquitous topic in material science. Al- though the concept is known for about 75 years, the origin of polarons is not yet fully elucidated. This thesis focuses on WO 3 as a well-known prototypical system for studying polarons, which inherent polaronic nature is linked to its remark- able electrical and chromic properties. The primary objective of this research is to provide a comprehensive atomistic description and understanding of polaron formation in WO 3 using first-principles density functional theory (DFT) calcula- tions. Additionally, the investigation explores the interactions between polarons and the possibility of bipolaron formation. Following a systematic strategy, we first extensively analyze the dielectric and lattice dynamical properties of WO 3 in both the room-temperature P 2 1 /n and ground-state P 2 1 /c phases. Our specific focus is on characterizing the zone-center phonons, which serve as the founda- tion for identifying the phonon modes involved in the polaron formation and charge localization process. Subsequently, we examine the impact of structural distortions on the electronic structure of WO 3 to elucidate the interplay between structural distortions and electronic properties, thereby laying the groundwork for understanding electron-phonon couplings. By incorporating these critical fac- tors, we address our primary research goals. The most common explanation for the polaron formation is associated with the electrostatic screening of the extra charge by the polarizable lattice. Here, we show that, even in ionic crystals, this is not necessarily the case. We demonstrate that polarons in this compound arise primarily from non-polar atomic distortions. We then unveil that this unexpected behavior originates from the undoing of distortive atomic motions, which lowers the bandgap. As such, we coin the name of anti-distortive polaron and validate its appearance through a simple quantum-dot model, in which charge localization is the result of balancing structural, electronic, and confinement energy costs. Then, we also study the polaron-polaron interaction and present the formation of the antiferromagnetic W 4+ bipolaronic state with relatively large formation energy. Our analysis of the W 4+ bipolaronic distortions on the global structure reveals the same behavior as in experiments where the highly distorted monoclinic phase transforms into a tetragonal phase as a function of doping. Additionally, leveraging our previous findings on asymmetric polaronic distortion and examin- ing different merging orientations, we stabilize the antiferromagnetic W 5+ -W 5+ bipolaronic state with an energy lower than the W 4+ state. This thesis clari- fies the formation of unusual medium-size 2D polarons and bipolarons in WO3,which might be relevant to the whole family of ABO 3 perovskites, to which WO 3 is closely related. The simplicity of the concept provides also obvious guidelines for tracking similar behavior in other families of compounds.

Abstract: Landfill mining refers to the re-circulation of resources from the previously deposited wastes–integrating resource recovery with traditional site remediation. Several resources that can be recovered include scrap metals, combustibles, and inert materials. In addition, land can be recovered or landfill void space can be liberated for future wastes. At present, landfill mining is still an emerging concept with few project implementations. Consequently, the assessments of its economic and climate implications are case study-specific, limiting the understanding of its potential in a wider geographical scope. This thesis aims to assess the economic performance and climate impact of landfill mining in Europe towards the development of sound strategies for implementation. Different project setups are assessed in relation to varying factors at the site level such as waste composition and landfill settings, and at the system level such as policy and market conditions and background material and energy. In doing so, a factor-based method is developed and applied to generate multiple scenarios (531, 441 scenarios per project setup) and determine the underlying important factors and their interrelations that drive the results. Such understanding is used to develop and discuss strategies for improvement by addressing relevant questions for specific stakeholders, including project investors (i.e., which landfill sites to prioritize?), landfill mining practitioners (i.e., how to set up such projects?), and policymakers (i.e., which policy instruments can effectively support such projects?). Results show that landfill mining is preferable in terms of climate than economy. Possible improvements are shown by internalizing thermal treatment of combustibles and extending fines residue utilization as construction aggregates. In relation to the choice of project setups, preferable site and system-level conditions are identified in general but it is also discussed that the plausibility of finding such conditions may be difficult at present. This steers the development of more tailored strategies on what can be done now by the landfill practitioners in terms of setting up projects under current policy and market conditions in specific regions, or what can be done by the policymakers in terms of implementing various policy instruments that can drive such changes at the system level. Through this thesis, the future of landfill mining research is guided towards addressing key challenges and potential solutions for improvement. Furthermore, this thesis highlights the role of assessment as a tool for learning and guiding the development of emerging concepts such as landfill mining.

Abstract: Socially responsible investments can be defined as an investment process that integrates ethical values and environmental protection, improving social conditions, and good governance into a traditional investment decision. This integration is mainly a consequence of the growing importance that investors give to environmental, social, and governance (ESG) criteria, resulting in more sustainable development. Also, in the real estate sector, increased attention is being paid to the contributions made to integrate economic, environmental, and social factors into decisions. The ESG framework looks closely at how companies are managed, and the impact related to their market value. The factors for investors’ focus are summarized as environmental, social, and governance. The term ESG was coined in a 2004 United Nations (UN) report titled “Who Cares Wins,” aimed at raising awareness regarding the importance of environmental, social, and corporate governance issues in financial markets. The ESG criteria’s specific purpose is to guide investors in recognizing sustainable investments without evaluating how sustainable the asset is or the investment value represented by sustainability. It is essential to underline that ESG does not take specific economic interests into account. The rationale behind this apparent gap is that investors investigate the economic aspects before investing. However, by not explicitly linking ESG and economic criteria, attractive investments are often misjudged and not implemented. For example, investments that only show their value in the longer term or indirectly influence value by achieving a higher retention rate among incumbent tenants, reducing or eliminating friction costs. A product–service system (PSS) refers to a market proposition (business model) that builds on a product’s traditional functionality by incorporating additional services. Although services are already offered, the PSS function is to link the service to a product. The service thereby supports the operation of the product and generates additional benefits. It encompasses the integrated solutions of products and services to satisfy customers' needs and generate maximum value. According to Sutanto et al., a PSS is designed to focus on sustainability characterized in three dimensions. 1. The economic dimension 2. The environmental dimension 3. The social dimension When discussing sustainability in this thesis, we use the criteria listed above related to socially responsible investments. The link between PSS and ESG is that a PSS focuses on creating a sustainable system, and ESG makes sustainability more visible to investors. Therefore, when PSS are recognized and implemented in buildings, they must be evaluated using ESG analysis methods. Product-Service Systems (PSS) try to find a way to offer services on top of a product. The product is essentially secondary to the result that is delivered from the services. For example, the modem (product) that a cable company provides will be of secondary importance to the connectivity (service). Alternatively, it will be less critical how heat is made (product) than the intended set point is achieved in the building. PSSs transform the supply of products into services. In doing so, the responsibility shifts from delivering a product (once only) to continuous service delivery. Therefore, it is in the best interest of the service provider to deliver the outcome of the service as efficiently (read: lowest cost) as possible. A direct consequence of this is that the service provider will want to use the product as efficiently as possible and as long as possible to reduce his costs. Therefore, the supplier will also want to recover and maximize the reuse of his product based on the same rationale. A positive impact on the environment and the used raw materials is thus to be expected. The whole process of servitization (transforming products into services) in real estate will positively impact the Economic, Environmental and Social factors. Therefore, demonstrating this proposition is the main objective of this thesis. Smart PSS is the same idea as Product-Service systems but in which the digitization of the services plays a key role. It will be shown that by digitizing services, a broader range can be offered. It will be demonstrated that products that provide services at the building level can, through their interconnectedness, also provide services to external systems (e.g. electricity grid, urban planning, mobility, ...). At the same time, digitizing the products and services will also underpin trust in the systems and allow for proper remuneration. In this PhD, different standard systems in a building, such as the reservation system, the water heater, or the fire detection system, are equipped with additional services. A PSS is often specifically designed to focus on economic, social, and environmental dimensions. These dimensions correspond to the investor’s examination as part of the ESG analysis before investing. As the PSS is often specifically designed to integrate sustainability, there is a close link between the sustainability performance of the PSS and the ESG criteria evaluated by the investor. Throughout the work, the owner is considered to be the user of the building. It is not the case that only an owner-user can generate cash flow. In essence, if they have sufficient rights to the underlying product, any building user can activate services that generate cash flow. In today's market, it is logical that this is viewed in the owner-user context as they will usually choose the products to be installed in larger technical installations. They may have previously used a PSS or choose to move to one. However, a building’s tenant could choose to lease out their meeting rooms if they are not contractually prohibited from doing so since, in practice, contracts have begun to prohibit certain services. For example, rental contracts that actively prohibit renting out a property through platforms such as Airbnb. Thus, the user’s function could potentially impact how the PSS is designed. This work does not explicitly explore the impact of this aspect. The owner-user is assumed throughout this manuscript. The second chapter describes the state of affairs concerning PSSs in a broad framework evolving towards focusing on the real estate sector. After which, in the second chapter, ESG and the link to real estate and how smart real estate (smart buildings) is missing from this evaluation are discussed in more detail. Chapter 3 shows from a fire alarm system, which was extended with an evacuation support system, the usefulness, and the risk of data. Further work was done to demonstrate the added value in terms of Economic, Environmental and Social factors of standard installations in buildings. In Chapter 4, a simple sanitary hot water boiler is extended with a service that allows controlling this boiler according to the status of the electricity grid (surplus or shortage of energy). The supply and demand of energy on the power grid must be equal at all times. By equipping a classic water heater (product) with additional intelligence (service), it becomes possible to adjust the energy use to the grid's needs. The grid operators are prepared to pay for this. This payment can be linked to different energy markets (long term market, spot market, ...). This study looked at the fee that would have to be paid when the adjustment of the energy use can be made instantaneously so that the fee must be settled according to the prices on the imbalance market. In chapter 5, we look at the impact of the service to rent out free spaces as co-working places on a broad market (external to the building), compared to a regular reservation system. By renting out unused workplaces on a broad market, the utilization of the existing patrimony will be higher. The demand for new square meters with the same function will decrease as the supply-demand curve changes, and so will the price. This makes it less interesting to build new buildings. Less construction of new buildings will result in fewer resources being used, which will positively affect the environment. In addition, fewer new buildings with an office function will leave more space for buildings with another function. Also, the city's infrastructure will be less burdened (roads, sewerage, electricity grid,...). In The Hague, the decreasing need for new square meters of office buildings can lead to more space for affordable housing, for which the city has a great need. Chapter 6 will frame the valuation of service as a real options method that gives an impetus to a general valuation methodology to value the flexibility that Smart PSS inherently has. Finally, this thesis demonstrates that (smart) PSSs impact real estate profitability, while positively influencing environmental and social factors. Further research and the limitations of the studies conducted are documented. This PhD concludes that Product-Service systems should break the silos between different stakeholders, resulting in a lower total cost of ownership of buildings in the longer term. This can only be achieved if the valuation of Product-Service systems is done correctly and is recognized by every stakeholder in the real estate process.