This book would be exciting to people that their interests broadly encompass condensed matter physics as a whole but lie in particular in the area of graphene-like 2D materials and in the area of superconductivity. The discovery of graphene opens up the possibility of new and exciting physics in a new class of materials. It was exhibited that single layer graphene can carry significant proximity supercurrents. Fabrication of graphene Josephson junctions enabled me to study the rare intersection of relativity and superconductivity. This initial work was extended to investigate 2D superconducting crystals of NbSe2. Our developed new mechanical exfoliation protocol enabled fabrication and measurement of superconductivity in several 4-point NbSe2 FETs devices. Results obtained on both graphene/NbSe2-FETs were encouraging and naturally suggest a number of extensions to this work. I would be excited to try and explore the combination of graphene and other 2d crystals by fabricating and characterizing such innovative prototype hybrid structures of these graphene-like 2D materials. I do believe that this research could play an important role in exploring new physics and device applications

A new experimental method – the "Stiffnessometer", is developed to measure elementary properties of a superconductor, including the superconducting stiffness and the critical current. This technique has many advantages over existing methods, such as: the ability to measure these properties while minimally disturbing the system; the ability to measure large penetration depths (comparable to sample size), as necessary when approaching the critical temperature; and the ability to measure critical currents without attaching contacts and heating the sample. The power of this method is demonstrated in a study of the penetration depth of LSCO, where striking evidence is found for two separate critical temperatures for the in-plane and out-of-plane directions. The results in the thesis are novel, important and currently have no theoretical explanation. The stiffnessometer in a tool with great potential to explore new grounds in condensed matter physics.

The confinement offered by superconducting nanostructures enables the study of the motion of individual Abrikosov vortices in reduced dimensions. At the present time, most superconducting nanostructures are fabricated from deposited films of metals, which are often polycrystalline or amorphous. The realization of a single-crystal nanostructure would provide the opportunity to explore the effects of the electronic band structure. Consider crystalline superconducting nanostructures of NbSe2. Questions such as the how the charge density wave order influences vortex pinning and the logarithmic vortex-vortex interaction, as well as how the crystal thickness dependence of the electronic band structure affects intrinsic vortex properties motivated our efforts to develop techniques to fabricate and measure superconducting nanostructures of 2D crystal NbSe2. Additionally, nanoscale transport devices are relevant to potential future superconducting electronics.In this dissertation, we begin by presenting a novel technique for the preparation of single-crystal nanostructures prepared from mechanically exfoliated few-layer crystals of NbSe2 using a process combining electron beam lithography and reactive plasma etching. Our technique allows for the preparation of ultra-thin, single-crystal superconducting nanostructures with a desired geometry for the study of vortex dynamics in extremely confined systems. A primary advantage of transport devices is the ability to directly manipulate individual vortices through the use of an applied current and other parameters.We first present magnetoresistance measurements on NbSe2 nanowires and show features related to vortex crossing, trapping, and pinning. The vortex crossing rate is found to vary non-monotonically with the applied field, which results in non-monotonic magnetoresistance variations in agreement with theoretical calculations in the London approximation. Above the lower critical field, Hc1, the crossing rate is also influenced by vortices trapped by sample boundaries or pinning centers, leading to sample-specific magnetoresistance patterns. We show that the local pinning potential can be modified by intentionally introducing surface adsorbates, making the magnetoresistance pattern a "magneto fingerprint" of the sample-specific configuration of vortex pinning centers in a superconducting nanowire.Building upon our work on NbSe2 nanowires, we next focus on NbSe2 nanoloops. The doubly-connected topology of nanoloops presents a unique opportunity for the manipulation of Abrikosov vortices; numerical calculations in the London limit suggest that an Abrikosov vortex can be trapped in a nanoloop above a critical magnetic field and generate a phase shift in the magnetoresistance oscillations. We measure magnetoresistance oscillations resulting from vortex crossing events in NbSe2 nanoloops and demonstrate experimentally that the crossing of vortices can be directed at a pair of constrictions in the loop, leading to more pronounced magnetoresistance oscillations than those in a uniform loop. We also observe for the first time a phase shift in the magnetoresistance oscillations resulting from vortex trapping in the nanoloop, and we manipulate the trapped vortex with an applied transport current. Results obtained in our NbSe2 devices provide a starting point for the manipulation of individual Abrikosov vortices, allowing further exploration of the fundamental properties of this topological object that will lead to a deeper understanding of the motion, including the quantum motion, of vortices. Longstanding, unresolved issues such as the Aharonov-Casher quantum interference of Abrikosov vortices may be solved.

This book elucidates fascinating electronic phenomena of unusual Bi2-square net in layered R2O2Bi (R: rare earth) compounds using two approaches: the fabrication of epitaxial thin films and the synthesis of bulk polycrystalline powders. The Bi2-square net compounds are a promising platform to explore exotic physical properties originating from the interplay between a two-dimensional electronic state and strong spin–orbit coupling; however, there are few reports on Bi2-square net compounds due to the instability of unusual electronic configurations. The book presents the development of synthetic routes for R2O2Bi compounds, such as novel solid phase epitaxy techniques and chemical control of crystal structure, demonstrating the intrinsic physical properties of Bi2-square net for the first time. The most notable finding is the successful induction of two-dimensional superconductivity in Bi2-square net with the coexistence of rich electronic phases. The book also discusses the superconducting mechanisms and the effect of R cation substitution in detail and describes the mechanical properties of Bi2-square net. These findings overturn the results of previous studies of R2O2Bi. The book sheds light on hidden layered compounds, representing a significant advance in the field.

This wide-ranging presentation of applied superconductivity, from fundamentals and materials right up to the details of many applications, is an essential reference for physicists and engineers in academic research as well as in industry. Readers looking for a comprehensive overview on basic effects related to superconductivity and superconducting materials will expand their knowledge and understanding of both low and high Tc superconductors with respect to their application. Technology, preparation and characterization are covered for bulk, single crystals, thins fi lms as well as electronic devices, wires and tapes. The main benefit of this work lies in its broad coverage of significant applications in magnets, power engineering, electronics, sensors and quantum metrology. The reader will find information on superconducting magnets for diverse applications like particle physics, fusion research, medicine, and biomagnetism as well as materials processing. SQUIDs and their usage in medicine or geophysics are thoroughly covered, as are superconducting radiation and particle detectors, aspects on superconductor digital electronics, leading readers to quantum computing and new devices.

This thesis presents first observations of superconductivity in one- or two-atomic-scale thin layer materials. The thesis begins with a historical overview of superconductivity and the electronic structure of two-dimensional materials, and mentions that these key ingredients lead to the possibility of the two-dimensional superconductor with high phase-transition temperature and critical magnetic field. Thereafter, the thesis moves its focus onto the implemented experiments, in which mainly two different materials thallium-deposited silicon surfaces and metal-intercalated bilayer graphenes, are used. The study of the first material is the first experimental demonstration of both a gigantic Rashba effect and superconductivity in the materials supposed to be superconductors without spatial inversion symmetry. The study of the latter material is relevant to superconductivity in a bilayer graphene, which was a big experimental challenge for a decade, and has been first achieved by the author. The description of the generic and innovative measurement technique, highly effective in probing electric resistivity of ultra-thin materials unstable in an ambient environment, makes this thesis a valuable source for researchers not only in surface physics but also in nano-materials science and other condensed-matter physics.

The goal of the series Physics and Chemistry of Materials with Layered Structures is to give a critical survey of our present knowledge on a large family of materials which can be described as solids containing molecules which in two dimensions extend to infinity and which are loosely stacked on top of each other to form three dimensional crystals. Of course, the physics and chemistry of these crystals are specific chapters in ordinary solid state science, and many a scientist hunting for new phenomena has in the past been disappointed to find that materials with layered structures are not entirely exotic. Their electron and phonon states are not two dimensional, and the high hopes held by some for spectacular dimensionality effects in superconductivity were shattered. Nevertheless, the structural features and their physical and chemical consequences singularize layered structures sufficiently to make them a fascinating subject of research. This is all the more true since they are met in insulators and semiconductors as well as in normal and superconducting metals. Although for the time being the series is intentionally limited to cover inorganic materials only, the many known organic layered structures may well be the subject of future volumes. Among the noteworthy peculiarities of layered structures, we mention specific growth mechanisms and crystal habits. Polytypism is very common and it is fasci nating indeed to find up to 240 different polytypes in the same chemical substance.

In this thesis the optical properties of quasi two-dimensional organic molecular crystals are investigated. Within this class of materials some systems are metallic, some are insulating due to charge-order, and others even become superconducting. The driving force behind the ground states is the di erent degree of e ective electronic correlations. Recent experimental and theoretical studies of strongly correlated materials suggest that uctuations of the ordered state may mediate superconductivity. The intention of this work is to prove the presence of such charge uctuations and reveal their relation to superconductivity. To do this, we investigated BEDT-TTF based organic conductors by optical spectroscopy covering a broad frequency (8-20000 cm 1 ) and temperature (1.8-300 K) range using FTIR- and THz-spectrometers. In addition, the transport properties are investigated by dc four-point contact measurements and microwave cavity perturbation technique."