Download or read book Low Temperature Scanning Tunneling Spectroscopy of Proximity Effect Junctions Formed on the Layered Superconductors NbSe2 and Bi2Sr2Ca1Cu2O8 written by Anthony D. Truscott and published by . This book was released on 1999 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scanning Tunneling Spectroscopy Studies of Multiband and Unconventional Superconductivity written by Igor Fridman and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Proximity Effect and Tunneling Spectroscopy of High temperature Superconductor semiconductor Hybrid Structures written by Parisa Zareapour and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Tunneling Spectroscopy Studies of Superconductors written by Basu Dev Oli and published by . This book was released on 2021 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt: In multiband superconductors, different bands at the Fermi surface contribute to the superconductivity with different magnitudes of superconducting gaps on different portions of the Fermi surface. Each band in a multiband superconductor has a condensate with an amplitude and phase that weakly interacts with the other bands' condensate. The coupling strength between the bands determines whether one or two superconducting transition temperatures are observed, and it is the key to many peculiar properties. In general, if there are two gaps of different magnitude, there are two different length scales associated with the suppression of these gaps in applied magnetic fields, for example. Therefore, effects of multigap superconductivity can be observed in superconducting vortices, which are twirls of supercurrents that are generated when a superconductor is placed in a magnetic field. Furthermore, the two superconducting order parameters in different bands are characterized by a magnitude and phase. In multiband superconductors, there are collective excitations corresponding to fluctuations of the relative phase of two order parameters, so-called the Leggett mode. The first material identified as multiband superconductor is Magnesium Diboride (MgB2) in 2001 with a critical temperature Tc of 39 K. MgB2 is a superconducting material with the highest transition temperature among all conventional BCS superconductors. It has two superconducting gaps \Delta_\pi ~ 2 meV and \Delta_\sigma\ ~ 7 meV and they arise from the existence of two bands \pi and \sigma bands of boron electrons. The discovery of superconductivity in MgB2 renewed interest in the field of multiband superconductivity. MgB2 has attracted many scientists' attention both for the fundamental importance of understanding the multiband superconductivity and possible applications such as magnets, power cables, bolometers, Josephson junction-based electronic devices, and radio-frequency cavities. Afterward, other materials have been identified as multiband superconductors such as NbSe2, the family of iron-based superconductors, heavy fermion superconductors, multilayer cuprates, borocarbides, etc. This dissertation uses tunneling experiments to highlight multiband superconductivity features in two systems, namely MgB2 thin films and ultrathin films of Pb. Further, we use multiple techniques to study a superconducting material, nitrogen-doped niobium, used for superconducting radio-frequency cavities. For the project on MgB2, MgB2/Native-Oxide/Ag planar junctions are fabricated and characterized down to 2.1 K and in the magnetic field parallel to the sample surface up to 6 Tesla. This work investigates how pairbreaking affects the magnitude and phase of the order parameter in a multiband superconductor. The tunneling spectra are analyzed in the framework of a two-band model developed by our theory collaborator Prof. Alex Gurevich, Old Dominion University. The model allows the extraction of the pair-breaking parameters among other quantities. The analysis shows that the order parameter in the ? band is quickly suppressed in the field, the ? band is cleaner than the ? band. The ratio of pairbreaking parameter in the ? band to the ? band rapidly increases at fields higher than ~0.1 T and then plateau at higher fields. This transition around 0.1 T magnetic field suggests a phase decoupling in the two bands of MgB2. Below the transition, the two bands are phase-locked, so mostly, the superconductivity in the ? band is affected, and after phase decoupling, both bands are affected by the applied field. These results are important for a basic understanding of multiband superconductors and the application implications of this material. This phase decoupling has a new and profound consequence on the superconducting state of a multiband superconductor that has been theoretically predicted and never observed experimentally. For the Pb project, ultrathin films of Pb in ultrahigh vacuum conditions are deposited by e-beam evaporation and characterized with low-temperature scanning tunneling microscopy and spectroscopy (STM/STS). The STM/STS allows measuring the electronic density of states with the highest spatial resolution down to atomic scale. The shape of a superconducting vortex core is determined by the superconducting gap and the Fermi velocity, and the STM allows to map anisotropies of these quantities spatially. The vortex cores of Pb film show a complex shape that evolves from triangular at short distances from the center to a six-fold symmetric star shape farther away from the center. These details are very subtle, and they can be highlighted only if one works within the clean limit (to avoid the averaging effect of the scattering) and by fabricating the heterostructure that pins the vortices spatially. The complex vortex core shape reflects the anisotropy of the two bands that contribute to superconductivity in this material. For the project on Niobium, cold and hot spots from nitrogen-doped Nb cutouts are characterized by low temperature scanning tunneling microscopy and spectroscopy (STM/STS) combined with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The radiofrequency (RF) measurements of the quality factor and temperature mapping on an N-doped Nb superconducting resonator cavity are carried out at Jefferson Laboratory before cutting out the samples. This work aims to identify possible sources of excess dissipation in hot spots and relate them to the surface chemical composition and superconducting properties. The temperature mapping revealed a strong effect of the cavity cooldown rate on the intensities of hot spots and their spatial distribution, which indicates a significant contribution of trapped vortices to the RF dissipation. SEM images acquired on the cold and hot spots using a secondary electron detector show absence of residual hydride scars and niobium nitrides on their surface. Angle-resolved XPS measurements on the native surface of these samples revealed higher oxidized Nb 3d states on the N-doped Nb cold spots, which is supported by XPS depth profiles done on the samples by Argon ion sputtering. Argon ion sputtering of oxidized Nb removes oxygen preferentially from Nb2O5 and diffuses to bulk, thickening the lower oxidation state layers. The proximity theory framework's tunneling spectra analysis suggests hot spots have stronger pairbreaking due to a weakly reduced pair potential, a thicker metallic suboxide layer, and a wide distribution of the contact resistance. STM imaging of vortex cores shows a triangular vortex lattice in both samples, and the coherence length is nearly the same in hot and cold spots. The experimental data analysis suggests weakly degraded superconducting properties at the surface of hot spot regions are not the primary sources of RF losses. Instead, they are the regions where vortices nucleate first and get trapped during cooling down. These experimental techniques and findings will be crucial in helping to qualify new recipes for SRF cavity production and to boost their performance.

Download or read book Schackert Michael PeterScanning Tunneling Spectroscopy on Electron Boson Interactions in Superconductors written by Schackert, Michael Peter and published by KIT Scientific Publishing. This book was released on 2015-03-23 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work describes the experimental study of electron-boson interactions in superconductors by means of inelastic electron tunneling spectroscopy performed with a scanning tunneling microscope (STM) at temperatures below 1 K. This new approach allows the direct measurement of the Eliashberg function of conventional superconductors as demonstrated on lead (Pb) and niobium (Nb). Preparative experiments on unconventional iron-pnictides are presented in the end.

Download or read book Resistive Anomalies in a Distributed Point Contact Proximity Effect Junction written by Matthew James Holcomb and published by . This book was released on 1991 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Low temperature scanning tunneling microscopy and spectroscopy of layered superconductors written by Christophe Renner and published by . This book was released on 1993 with total page 85 pages. Available in PDF, EPUB and Kindle. Book excerpt: Il fut utilisé pour une étude topographique et spectroscopique du supraconducteur classique 2H-Nb1-xTaxSe2(x=0,0.03,0.1,0.15 et 0.2) et du supraconducteur à haute température critique Bi2Sr2CaCu2O8.

Download or read book The Proximity Effect in High Tc Superconductor ferromagnet Bilayers Studied by Scanning Tunneling Spectroscopy written by Itay Asulin and published by . This book was released on 2009 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Tunneling Spectroscopy on an Atomically Thin Transition Metal Dichalcogenide Superconductor written by Egon Sohn and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Two dimensional (2D) materials have become very popular in the last decade. Among the many available 2D materials, 2H-NbSe2, which is one compound of the transition metal dichalcogenide (TMD) family, represents the 2D superconductors. The TMDs are unique in a sense that when the bulk is thinned down to a monolayer limit, inversion symmetry is broken. Together with the strong spin-orbit coupling, spin degeneracy is broken in each band and leads to electron spins pinned in out-of-plane direction, which are opposite in direction for opposite momentum. These are called Ising spins. Unlike the conventional superconductors which freely rotating spins pair, the Cooper pairs in 2D-NbSe2 are formed by Ising spins. This results in unconventional superconducting properties. We take advantage of the unique aspect of atomically thin superconductors which is the quenched orbital depairing effect under in-plane magnetic field and study the spin properties of the superconducting state. In the first part of this dissertation (Chapter 3), we study the superconducting properties of 2D-NbSe2 under large in-plane magnetic field. We characterize the magnetic field versus temperature phase diagram of one- to three-layer NbSe2 by electrical transport measurement and find an enhanced upper critical field, several times larger than the Pauli paramagnetic limit. By fitting the results to the pair breaking equation, we confirm large spin-orbit field in 2D-NbSe2. We fabricate planer tunneling junctions and measure differential conductance spectra under in-plane magnetic field. The superconducting gap is obtained by fitting the data with the Blonder-Tinkham-Klapwijk (BTK) model. We find that there is a second-order transition in contrast to first-order transition observed in conventional superconductors. The enhanced upper critical field and the second-order phase transition both suggests finite spin susceptibility in the superconducting state which originates from the mixed spin singlet-triplet Cooper pair wave function present in noncentrosymmetric superconductors. In the second part (Chapter 4), we study the in-plane magnetic field response of the two superconducting gaps of 2D-NbSe2 and show there is a possible field driven nodal phase transition in the [gamma]-pocket superconducting order parameter. This is achieved by fabricating high-quality tunneling devices in which the differential conductance spectrum reflects the density of states. We were able to fit the data with a two-gap Bardeen-Cooper-Schrieffer density of states and identify the two superconducting gaps in 2D-NbSe2. The distinct behavior of the two superconducting gaps are explained in terms of the different spin-orbit coupling strength of the K- and [gamma]-pocket, which is also consistent with earlier theoretical studies that suggest a magnetic field driven nodal superconducting phase. We also discuss limitations in our measurement that prevents us from discerning between a nodal and a fully gapped superconducting phase in high magnetic field. In the last part (Chapter 5), we construct tunneling devices with either a magnetic barrier or a magnetic material and observe a novel two-fold symmetry in the differential conductance spectra. We fit the measured spectra with a two-gap BTK model and find that the weight of the two gaps and the superconducting order parameter depends on in-plane magnetic field direction and field strength. Our observation is explained in terms of competing superconducting channels which stabilizes by small symmetry breaking fields such as strain or external magnetic field.

Download or read book Magnetic Superconductors written by A. V. Narlikar and published by Nova Science Pub Incorporated. This book was released on 2003 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume focuses on the topical area of magnetic superconductors. Rutheno cuprates and quaternary borocarbides are the two frontal materials forming the mainstay of the book. The authors are noted for their pioneering contribution in the field. In all, there are 6 chapters written by 18 researchers from 6 countries taking stock of frontal issues of both experiment and theory. Chapter headings: Phase Separation, Magnetism and Superconductivity in Rutheno-Cuprates; Coexistence of Superconductivity and Magnetism in R2-xCexRuSr2Cu2O10-d(R=Eu and Gd); Magneto-Superconductivity in Rutheno-Cuprates RuSr2GdCu28-d (Ru-1212) AND RuSr2(Gd0.75 Ce0.25)2Cu2O10-d (Ru-1222): A Critical Review; Therman Conductivity in Magnetic Superconductors; Magnon Specific Heat of the Antiferromagnetic Superconductors RNi2B2C [R=Tm, Er, Ho, Dy]; On the Role of the Electronic Structure in the Properties of Pseudo Quaternary Borocarbides.

Download or read book Quantum Fluids and Solids written by S. Trickey and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt: The second International Symposium on Quantum Fluids and Solids came to pass during 23-27 Jan. 1977 as the fourth and con cluding part of the seventeenth consecutive running of the Sanibel Symposium Series. With approximately 120 participants from eleven countries (including, for the first time, the USSR), we found it easy to obtain a selection of papers which was fairly comprehen sive. Indeed, our problem was an embarrassment of riches; in spite of our solemn vows not to crowd the schedule, we ended up with an intense program! By far, the majority of the papers pre sented are represented in this volume. We are indebted to many persons and organizations for their contributions to the Symposia. First, we thank Prof. Per-Olov Lowdin, Director of the Quantum Theory Project and originator of the Sanibel Symposia. Without his patient, indulgent cooperation our task would have been vastly more difficult. We are grateful to Prof. F. Eugene Dunnam, Chairman of the Dept. of Physics and Astronomy, for providing Departmental support of our initial or ganlzlng expenses. Approximately one-half of the total cost of the Symposium was borne by a joint grant from the National Science Foundation and the U. S. Air Force Office of Scientific Research. We thank the program officers, Dr. C. Satterthwaite and Dr. D.

Download or read book Soft Interfaces written by Pierre Gilles de Gennes and published by Cambridge University Press. This book was released on 1997-04-28 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt: An impressionistic tour of the physics of soft interfaces by Nobel Laureate Pierre Gilles de Gennes.

Download or read book International Scientific Affairs written by United States. Department of State. Office of Media Services and published by . This book was released on 1963 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Condensed Matter and Materials Physics written by National Research Council and published by National Academies Press. This book was released on 2008-01-21 with total page 285 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of transistors, the integrated circuit, liquid-crystal displays, and even DVD players can be traced back to fundamental research pioneered in the field of condensed-matter and materials physics (CMPP). The United States has been a leader in the field, but that status is now in jeopardy. Condensed-Matter and Materials Physics, part of the Physics 2010 decadal survey project, assesses the present state of the field in the United States, examines possible directions for the 21st century, offers a set of scientific challenges for American researchers to tackle, and makes recommendations for effective spending of federal funds. This book maintains that the field of CMPP is certain to be principle to both scientific and economic advances over the next decade and the lack of an achievable plan would leave the United States behind. This book's discussion of the intellectual and technological challenges of the coming decade centers around six grand challenges concerning energy demand, the physics of life, information technology, nanotechnology, complex phenomena, and behavior far from equilibrium. Policy makers, university administrators, industry research and development executives dependent upon developments in CMPP, and scientists working in the field will find this book of interest.

Download or read book Magnetic Properties of Antiferromagnetic Oxide Materials written by Lamberto Duò and published by John Wiley & Sons. This book was released on 2010-04-16 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt: This first focused treatment on a hot topic highlights fundamental aspects as well as technological applications arising from a fascinating area of condensed matter physics. The editors have excellent track records and, in light of the broadness of the topic, retain the focus on antiferromagnetic oxides. They thus cover such topics as dichroism in x-ray absorption, non-magnetic substrates, exchange bias, ferromagnetic-antiferromagnetic interface coupling and oxide multilayers, as well as imaging using soft x-ray microscopy. The result is a very timely monograph for solid state physicists and chemists, materials scientists, electrical engineers, physicists in industry, physical laboratory technicians, and suppliers of sensors.