Superconductors are important to study due to their many applications. Superconductivityarises when electron pairs, so-called Cooper pairs, form in the material.To understand the mechanism behind the formation of the Cooper pairs, the pairingsymmetry, described by the order parameter, must be found. One method to experimentallydetermine the order parameter is through quasi-particle interference.Quasi-particle interference (QPI) is a real space perturbation due to a defect andcan be experimentally imaged using scanning tunneling microscopy (STM), wherean atomic sized tip is scanned over a surface at a bias measuring the tunneling currentthrough the sample surface. QPI can also be theoretically calculated using atight-binding model describing the electronic structure and then using an interpolationbetween unit cells using wave functions to carry intra-unit cellular information,so-called Continuum QPI (CQPI). This report studies the influence of different superconductingorder parameters in a one-band cuprate-like material on theoreticallycalculated phase-referenced Fourier transformed CQPI (PRFT-CQPI). The resultsshow that this method gives qualitatively distinct results depending on the ordersymmetry, suggesting that it can be used to experimentally determine the superconductinggap symmetry. The results are also compared with experiment and withpreviously published CQPI calculations.

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This report presents the significant advancements made in the UppASD software package, a tool for atomic spin dynamics simulations, through the integration of GPU acceleration. Originally developed at Uppsala University, UppASD primarily utilized CPU-based computations. This project aimed to enhance its computational efficiency and capability by extending and rigorously evaluating its GPU-based implementation. The focus was on integrating a variety of magnetic interactions, including tensorial coupling, anisotropy models, and the Dzyaloshinskii-Moriya interaction, into the GPU framework. We also assessed the impact of GPU acceleration on the calculation of key observables. The methodology involved a comprehensive evaluation of the existing code structure, meticulous debugging, and performance benchmarking. This report details the development process, highlights the challenges encountered, and provides insights into future directions for the UppASD project. / <p>Held internally sharing the progress made.</p>

Performance and energy consumption of large-scale computing infrastructures could be improved significantly by adoption of superconducting electronics. Rapid single flux quantum (RSFQ) circuits with logic based on the vortex state in Type II superconductors were first demonstrated several decades ago and as of now, research focusing on developing modern superconducting electronic components operating on the level of a single Abrikosov vortex is ongoing, where RSFQ serves as a convenient reference point. The main focus of this project was one crucial aspect for such components, namely reliable manipulation of vortex dynamics under transport current. A set of realistic and relevant micron scale geometries of superconducting thin films with a circular vortex trap were simulated by obtaining numerical solutions of time-dependent Ginzburg-Landau equations in two spatial dimensions. Within the scope of this work, successful manipulation of vortex dynamics means being able to perform each of the following actions on-demand: introduce one vortex into the device, pin it to the trap, remove it from the device. Current and time-dependent behaviour of vortices in different device geometries was studied and an important role of seemingly small changes in geometric parameters was established. Certain geometric configurations were discovered to be inherently more favourable for deterministic control of vortex dynamics, while others were identified as inherently unfavourable. Practically conceivable methods to separate between the two were introduced. Repeated sequences of "write" (trapping a vortex) and "erase" (removing a vortex) operations with square waves of transport current tailored to a particular device geometry were simulated as a demonstration of successful vortex manipulation. Findings of this thesis are expected to improve the success rate of physically conducted experiments within the area of superconducting vortex-based electronics.

This report presents the redesign of the Ultra-Low Energy Implanter (LEION) at the Tandem Laboratory. The primary objectives were to evaluate the current configuration of LEION, identify potential improvements through simulations, and enhance the control software, SIMBA. The studyinvolved detailed simulations of ion trajectories within the LEION system using the SIMION software, focusing on the steering plates and the sample holder. Key findings highlighted limitationsin the current setup, including the steering plates configuration. Which were addressed througha proposed new design that would solve many of LEION’s current shortcomings by incorporating an additional electromagnetic lens into the system. Upgrades to the SIMBA interface aimed tointegrate additional functionalities, streamline beam alignment, and consolidate control systemsto improve user accessibility. The redesigned system demonstrated improved performance insimulations, providing a more even ion distribution and enhanced usability. This project offerssignificant insights into optimising low-energy ion implantation systems and presents a frameworkfor future developments in this field.

An important, but also difficult, research field in condensed matter physics is that of strongly correlated systems. This thesis considers two topics in this field. The first topic is disorder and frustration in spin models. The introduction of disorder into quantum spin chains creates a complex problem. The ground state of the random-bond spin-1 Heisenberg chain is studied by means of stochastic series expansion quantum Monte Carlo simulation, applying the concept of directed loops. It is found that this system undergoes a phase transition to the random-singlet phase if the bond disorder is strong enough. Further a frustrated spin system is investigated. The frustration is introduced by having spins positioned on a triangular lattice. Performing a quantum Monte Carlo simulation for such a frustrated lattice leads to the occurrence of the infamous sign problem. This problem is investigated and it is shown that it is possible to use a meron cluster approach to reduce its effect for some specific models. The second topic concerns atomic condensates in optical lattices. A system of trapped bosonic atoms in such a lattice is described by a Bose-Hubbard model with an external confining potential. Using quantum Monte Carlo simulations it is demonstrated that the local density approximation that relates the observables of the unconfined and the confined models yields quantitatively correct results in most of the interesting parameter range of the model. Further, the same model with the addition that the atoms carry spin-1 is analyzed using density matrix renormalization group calculations. The anticipated phase diagram, with Mott insulating regions of dimerized spin-1 chains for odd particle density, and on-site singlets for even density is confirmed. Also an ultracold gas of bosonic atoms in an anisotropic two dimensional optical lattice is studied. It is found that if the system is finite in one direction it exhibits a quantum phase transition. The Monte Carlo simulations performed show that the transition is of Kosterlitz-Thouless type. / QC 20100628

This thesis describes experimental investigation of thin films made of diluted Pt 1-x Ni x ferromagnet alloy and Nb-Pt 1-x -Nb Josephson junctions. Such Hybrid Superconductor-Ferromagnet (S-F) Structures are of significant interest because of the new physics involved and possible applications in low temperature and spintronic devices. In many cases, such devices require components with small monodomain ferromagnetic layers, which requires development of specific nano-fabrication techniques. Pt 1-x Ni x alloy is used as the ferromagnet layer due to very good solubility of the two components which results in homogeneous diluted ferromagnet. Systematic analysis of both chemical composition, and ferromagnetic properties of Pt 1-x Ni x thin films for Ni concentrations ranging between 0 and ~70 at.% is performed. The energy-dispersive X-ray spectroscopy (EDS) technique is employed to study chemical composition of Pt 1-x Ni x thin films. To eliminate possible errors during EDS characterization, EDS is used with different electron beam energies, different electron beam incident angles and on the free standing Pt 0.59 Ni 0.41 flakes. Ferromagnetic properties of Pt 1-x Ni x thin films are analyzed by studying the anomalous Hall effect. The Curie temperature of Pt 1-x Ni x films decreases in a non-linear manner with the Ni concentration and has the onset at ~27 at.% of Ni. It is observed that the critical concentration of Ni is lower and the Curie temperature is higher than it had been observed early for the bulk PtNi alloys. The 3D Focused ion Beam Nanosculpturing is used to fabricate nanoscale S-F-S Josephson junctions providing the uniform, monodomain structure of the ferromagnet layer within the junction. The detailed studies of S-F-S Josephson junctions are carried out depending on the size of junction, thickness and composition of the ferromagnet layer. The obtained Fraunhofer modulation of the critical current as a function of in-plane magnetic field serves as evidence for uniformity of the junction properties and monodomain structure of ferromagnet layer. The junction critical current density decreases in spin glass state with increasing Ni concentration. In the ferromagnetic state the maximum current density of the junction starts to increase. The latter is attributed to switching into the pi state as a function of Ni concentration. Simultaneously it is observed that the critical current can completely disappear presumably as the result of stray fields from the F layer in contact leads. The Josephson junction is used as a phase sensitive detector for analysis of vortex states in mesoscopic superconductors. By changing the bias current at constant magnetic field the vortices can be manipulated and the system can be switched between two consecutive vortex states. A mesoscopic superconductor can thus act as a memory cell in which the junction is used both for reading and writing information (vortex).

<p>The aim with this essay is to find out what the expected changes in the subject physics will lead to for teachers and their pupils in “gymnasiet”. The new fields we have chosen to focus on are electronic structure of condensed matter, nanotechnology and material physics. By studying earlier used curricula and textbooks, we illustrate what teachers may have come into contact with in their teaching careers. The main focus lies on what teachers claim to know about the fields mentioned above and if there is a need for further education. Our results indicate that teachers in general feel insecure about their knowledge of these fields and that further education is desirable. The studied group of teachers also have wishes on how to form possible further education.</p> / <p>Syftet med arbetet är att undersöka vad de väntade förändringarna av fysikämnet kommer att innebära för fysiklärare och elever i den svenska gymnasieskolan. De nya områden vi har valt att fokusera på är den kondenserade materiens elektronstruktur, nanoteknologi samt materialfysik. Genom studier av äldre kursplaner och läroböcker ger vi en bild av vad lärarna kan ha stött på tidigare i deras fysikundervisning. Tyngdpunkten ligger i vad lärarna anser sig kunna inom de ovan nämnda områdena samt om det föreligger något fortbildningsbehov. Våra resultat tyder på att lärarna i allmänhet känner en stor osäkerhet inför dessa nya områden och att fortbildning är önskvärt. De lämnar även önskemål om utformning av en eventuell fortbildning.</p>

The aim with this essay is to find out what the expected changes in the subject physics will lead to for teachers and their pupils in “gymnasiet”. The new fields we have chosen to focus on are electronic structure of condensed matter, nanotechnology and material physics. By studying earlier used curricula and textbooks, we illustrate what teachers may have come into contact with in their teaching careers. The main focus lies on what teachers claim to know about the fields mentioned above and if there is a need for further education. Our results indicate that teachers in general feel insecure about their knowledge of these fields and that further education is desirable. The studied group of teachers also have wishes on how to form possible further education. / Syftet med arbetet är att undersöka vad de väntade förändringarna av fysikämnet kommer att innebära för fysiklärare och elever i den svenska gymnasieskolan. De nya områden vi har valt att fokusera på är den kondenserade materiens elektronstruktur, nanoteknologi samt materialfysik. Genom studier av äldre kursplaner och läroböcker ger vi en bild av vad lärarna kan ha stött på tidigare i deras fysikundervisning. Tyngdpunkten ligger i vad lärarna anser sig kunna inom de ovan nämnda områdena samt om det föreligger något fortbildningsbehov. Våra resultat tyder på att lärarna i allmänhet känner en stor osäkerhet inför dessa nya områden och att fortbildning är önskvärt. De lämnar även önskemål om utformning av en eventuell fortbildning.

Transparent conducting oxides (TCOs) are an important class of materials with many applications such as low emissivity coatings, or transparent electrodes for photovoltaics and flat panel displays. Among the possible TCO materials, Al-doped ZnO (AZO) is studied due to its relatively low cost and abundance of the raw materials. Thin films of AZO are commonly produced using physical vapour deposition techniques such as magnetron sputtering. However, there is a problem with the homogeneity of the films using reactive direct current magnetron sputtering (DCMS). This homogeneity problem can be related to the bombardment of the growing film with negative oxygen ions, that can cause additional acceptor defects and the formation of insulating secondary phases. In this work AZO films are deposited by high power impulse magnetron sputtering (HiPIMS), a technique in which high instantaneous current densities are achieved by short pulses of low duty cycle. In the first part of this thesis, the possibility to improve the homogeneity of the deposited AZO films by using HiPIMS is demonstrated. This improvement can be related to the high instantaneous sputtering rate during the HiPIMS pulses, so the process can take place in the metal mode. This allows for a lower oxygen ion bombardment of the growing film, which can help to avoid the formation of secondary phases. Another problem of AZO is the stability of the properties in humid environments. To assess this problem, the degradation of the electrical properties after an aging procedure was investigated for films deposited by both DCMS and by HiPIMS. A method was proposed, to restore the properties of the films, using a low temperature annealing under N2 atmosphere. The improvement of the electrical properties of the films could be related to a diffusion process, where water is diffusing out of the films. Then, the influence of the substrate temperature on the properties of AZO films deposited by HiPIMS was studied. The electrical, optical and structural properties were found to improve with increasing substrate temperature up to 600 ◦C. This improvement can be mostly explained by the increase in crystalline quality and the annealing of defects. Finally, the deposition of AZO films on flexible PET substrates was investigated. The films are growing as a thick porous layer of preferentially c-axis oriented columns on top of a thin dense seed layer. The evolution of the sheet resistance of the films after bending the films with different radii was studied. There is an increase in the sheet resistance of the films with decreasing bending radius, that is less pronounced for thicker films.