Electron Tunneling and Point Contact Andreev Reflection Studies of Superconductors PDF Download
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Author: Wenqing Dai
Publisher:
ISBN:
Category :
Languages : en
Pages : 155
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Book Description
Author: Wenqing Dai
Publisher:
ISBN:
Category :
Languages : en
Pages : 155
Get Book Here
Book Description
Author: Xin Lu
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Point-contact Andreev reflection spectroscopy (PCARS) and planar tunneling spectroscopy are used to investigate the density of states and superconducting gap structure of several novel superconducting systems. Theoretical and experimental background is given with an emphasis on PCARS as applied to various unconventional superconductors, such as NbSe$_2$, the borocarbide family RNi$_2$B$_2$C (R=Lu, Y) and the recently-discovered, iron-based superconductors AFe$_2$As$_2$ (A=Ba, Sr) with both hole and electron doping. The superconducting gap distribution observed from point-contacts on NbSe$_2$, with energies between 0.9 and 1.5 meV at 2 K, is consistent with the multigap scenario claimed by other experiments. The superconducting gap follows the BCS temperature dependence. PCARS probes a small gap anisotropy in both LuNi$_2$B$_2$C and YNi$_2$B$_2$C for the three major crystallographic orientations, while point-nodes are reported to exist in textit{a} and textit{b} axes and predicted to originate from the antiferromagnetic fluctuations due to nesting structure on the 17th band Fermi surface. This can be explained by the other Fermi surface sheets, with $Deltageq$2.1 meV in [100] direction, masking the point-node feature and resulting in a small gap anisotropy, as observed in our PCARS. A large tunneling cone in PCARS measurements, which would smear the differences in three directions, may be another origin of the observed small gap anisotropy. For the Fe-122 family of the iron-based superconductors, Andreev reflection is present for PCARS on (Ba$_{0.6}$K$_{0.4}$)Fe$_2$As$_2$ and Ba(Fe$_{0.9}$Co$_{0.1}$)$_2$As$_2$ crystals but measured conductances are distinct. A V-shape conductance valley (VCV) feature is observed for point-contacts on Sr(Fe$_{0.9}$Co$_{0.1}$)$_2$As$_2$ and (Sr$_{0.6}$Na$_{0.4}$)Fe$_2$As$_2$ crystals. This VCV feature is also observed for the non-superconducting parent compound BaFe$_2$As$_2$ and the superconducting (Ba$_{0.6}$K$_{0.4}$)Fe$_2$As$_2$ crystals. The coexistence of phase-separated magnetic and superconducting orders on the mesoscopic scale is considered to explain the range of behaviors in the superconducting samples.
Author: Yu.G. Naidyuk
Publisher: Springer
ISBN: 1475762054
Category : Science
Languages : en
Pages : 303
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Book Description
Various experimental techniques for point contact production are described. Examples of point-contact spectra are presented for pure metals, alloys and compounds, as well as for semimetals and semiconductors, heavy fermion systems, Kond-lattices, mixed valence compounds and more. Superconducting point contacts are considered in respect to Andreev reflection and Josephson effects. Special attention is paid to contact conductance fluctuation, and new trends of research are outlined.
Author: Yasuhiro Asano
Publisher: Springer Nature
ISBN: 981164165X
Category : Technology & Engineering
Languages : en
Pages : 137
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Book Description
This book offers a primer on the fundamental theory of Andreev reflection, a fundamental process in the motion of a Cooper pair, which dominates low-energy electronic transport properties in superconductor junctions including differential conductance and Josephson current. The book concisely describes how Andreev reflection impacts the low-energy physics of electronic transport especially in topologically non-trivial superconductor junctions. In addition, it includes an introduction to topological superconductors, covering topological classification, chiral and helical superconductors, and topological edges. The book is based on the author’s lecture notes, used in his intensive lectures and while supervising his upper undergraduate and early graduate students. To fully benefit from this concise primer, readers only need an undergraduate background in quantum mechanics and statistical mechanics. Further, by highlighting Josephson junctions of topological superconductors, the book offers readers a glimpse into cutting-edge topics.
Author: Kiril Borisov
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Alexander Gabovich
Publisher: BoD – Books on Demand
ISBN: 9535121332
Category : Technology & Engineering
Languages : en
Pages : 282
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Book Description
The chapters included in the book describe recent developments in the field of superconductivity. The book deals with both the experiment and the theory. Superconducting and normal-state properties are studied by various methods. The authors presented investigations of traditional and new materials. In particular, studies of oxides, pnictides, chalcogenides and intermetallic compounds are included. The superconducting order parameter symmetry is discussed and consequences of its actual non-conventional symmetry are studied. Impurity and tunneling effects (both quasiparticle and Josephson ones) are among topics covered in the chapters. Special attention is paid to the competition between superconductivity and other instabilities, which lead to the Fermi surface gapping.
Author: A. V. Narlikar
Publisher: Oxford University Press
ISBN: 0198738161
Category : Science
Languages : en
Pages : 641
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Book Description
Mesoscopic superconductors achieve a level of smallness that reveals the dominance of strange quantum effects. In a world driven by the miniaturization of electronic device technology, small superconductors acquire great relevance and timeliness for the development of ground breaking novel quantum devices.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 6
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Book Description
While the initial goal of the proposal was to concentrate on the study of point contact dots to HTSC. our initial measurements showed that surface preparation and impurities will be a major factor in determining the results, especially if we want to study the crossover from Andreev to tunneling behavior. We therefore launched a thorough study of the effects of single impurities and surface modifications on the tunneling spectra in HTSC. Our findings include the understanding of zero-bias anomalies as coming from point-impurities and the transition from spin-gap to superconducting-gap behavior as a function of strength of surface modification.
Author: Anton Zeilinger
Publisher: World Scientific
ISBN: 9789810248185
Category : Computers
Languages : en
Pages : 540
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Book Description
Quantum information theory has revolutionised our view on the true nature of information and has led to such intriguing topics as teleportation and quantum computation. The field - by its very nature strongly interdisciplinary, with deep roots in the foundations both of quantum mechanics and of information theory and computer science - has become a major subject for scientists working in fields as diverse as quantum optics, superconductivity or information theory, all the way to computer engineers.
Author: N. Bontemps
Publisher: Springer Science & Business Media
ISBN: 9401109745
Category : Science
Languages : en
Pages : 330
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Book Description
One of the most spectacular consequences of the description of the superfluid condensate in superfluid He or in superconductors as a single macroscopic quantum state is the quantization of circulation, resulting in quantized vortex lines. This book draws no distinction between superfluid He3 and He4 and superconductors. The reader will find the essential introductory chapters and the most recent theoretical and experimental progress in our understanding of the vortex state in both superconductors and superfluids, from lectures given by leading experts in the field, both experimentalists and theoreticians, who gathered in Cargèse for a NATO ASI. The peculiar features related to short coherence lengths, 2D geometry, high temperatures, disorder, and pinning are thoroughly discussed.
