Download or read book Electrical Transport Studies Of Topological Insulator Bi2te3 Nanotubes written by Renzhong Du and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological insulators (TIs) are bulk insulators with unusual gapless metallic surface states protected by time reversal symmetry. The topological surface states are expected to yield unique phenomena, such as spin-momentum locking and the suppression of non-magnetic backscattering. The surface states with a Dirac cone like dispersion relation have been observed directly using Angle-resolved photoemission spectroscopy (ARPES). Their signatures in electrical transport properties have also been reported although the transport behaviors are complicated by the fact that the samples often have dominating conduction from bulk channels due to high carriers density from impurity states. It is theoretically predicted that the surface states are robust against strong disorders, but it has not been tested experimentally. Bi2Te3, a member of the Bi2Se3 family, has been demonstrated to be a promising candidate of 3D topological insulators. In this work, various transport studies have been carried out on Bi2Te3 nanotubes with strong disorders. As essentially narrow gap semiconductors with band gaps of 100 to 300 meV, the Bi2Se3 family often have conducting bulk due to impurity doping and lattice imperfection, such as vacancies, dislocations, and defects. Several approaches have been applied to reduce bulk conductivity. The first one is to compensate bulk carriers by chemical doping or field effect, which drags Fermi level back to bang gap. Another is to fabricate nano-scale samples with enhanced surface-to-volume ratio, and effectively reduce the weight of bulk conduction. In our work we have prepared Bi2Te3 nanotubes by solution phase method utilizing Kirkendall effect. Due to the nature of this process, polycrystalline Bi2Te3 nanotubes form with extremely strong disorders. In this way, bulk carriers are strongly localized and the samples are brought from a heavily doped band semiconductor to the regime of Anderson insulator. We have demonstrated that the bulk conductance of the nanotubes is truly insulating and characterized by Mott Variable Range Hopping (VRH) mechanism. Despite the strongly disordered bulk channel, Aharonov-Bohm (AB) like oscillations in magnetoconductance have been observed on the nanotubes at low temperatures. The conductance oscillations differ from those on either ballistic or diffusive normal metals. With the combination of theoretical analysis and simulations, we show that these oscillations originate from the outer surface states of the nanotubes. Their behaviors are consistent with the prediction of the "anomalous AB effect" of topological surface states. In comparison with published work on clean TIs, we provide a direct demonstration of the fundamental aspect of topological surface states, namely their robustness to time-reversal invariant disorder. The interplay between a TI and a superconductor (SC) is another interesting topic to explore the exotic behaviors of topological surface states. For example, proximity induced superconductivity on topological insulators leads to the new phase of topological superconductivity, which serves a host of Majorana fermions. On the other hand, proximity effect can be suppressed on topological surface states, with the presence of an anomalous resistance increase. We report a systematical study of the anomalous resistance increase on Bi2Te3 nanotubes with superconducting Nb electrodes. With various measurement strategies, we show that this resistance increase behavior occurs on the nanotubes rather than from SC/TI interface effects. It is induced from the contact with superconducting Nb without requiring current flowing through the Nb. The characteristic length of the anomalous resistance increase reaches as far as 450 nm at low temperature. Gate experiments confirm that the surface states of the nanotubes are responsible for this effect. Our results indicate that a new charge correlation may establish on the surface states of Bi2Te3 nanotubes under the proximity of superconductor, suggesting further studies on this subject to explore the underlying physical origins, both theoretically and experimentally.

Download or read book Optical and electrical properties of topological insulator Bi2Se3 written by Jiajun Zhu and published by diplom.de. This book was released on 2017-07-12 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological insulator is one of the hottest research topics in solid state physics. This is the first book to describe the vibrational spectroscopies and electrical transport of topological insulator Bi2Se3, one of the most exciting areas of research in condensed matter physics. In particular, attempts have been made to summarize and develop the various theories and new experimental techniques developed over years from the studies of Raman scattering, infrared spectroscopy and electrical transport of topological insulator Bi2Se3. It is intended for material and physics researchers and graduate students doing research in the field of optical and electrical properties of topological insulators, providing them the physical understanding and mathematical tools needed to engage research in this quickly growing field. Some key topics in the emerging field of topological insulators are introduced.

Download or read book Electrical Transport Studies of 3D Bi based Topological Insulators written by Hongchao Liu and published by . This book was released on 2014 with total page 79 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Electrical Transport Studies of 3D Topological Insulator Bi2Se3 and Related Specific Structures written by Huachen Zhang and published by . This book was released on 2018 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Topological Insulators written by Jeroen B. Oostinga and published by Elsevier Inc. Chapters. This book was released on 2013-11-23 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: The discovery of topological insulators as a new state of matter has generated immense interest in this new class of materials. Three-dimensional (3D) topological insulators are characterized by the presence of an odd number of families of Dirac fermions—ideally one- at each of their surfaces. Angle-resolved photoemission experiments have demonstrated the presence of the expected Dirac fermions, but it is clear that to explore the electronic properties of these systems, transport measurements in many different device geometries are called for, just as it has been the case for Dirac fermions in graphene. In this chapter we review the status of transport studies through 3D topological insulators as of early summer 2012, after that a first generation of experiments has been performed. The results provide many different indications of the presence of surface fermions, as well as evidence of their Dirac nature. However, no textbook “manifestation” of surface Dirac fermions has been reported so far in these materials. Indeed, experiments also show that investigations are severely hampered by the material quality in most cases, because of the effect of high conductivity in the bulk, of low carrier mobility, of technical difficulties hampering device fabrication, and other reasons. In this chapter, we attempt to give a balanced overview of the work done during this first period and of the results obtained, stressing the implications and the limits of many of the observations that have been reported in the literature.

Download or read book Topological Insulators written by Inamuddin and published by Materials Research Forum LLC. This book was released on 2024-01-15 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt: A topological insulator is an area that has yet to be fully explored and developed. The charge-induced bandgap fluctuation in the best-known bismuth-chalcogenide-based topological insulators is approximately 10MeV in magnitude. The major focus has shifted to the investigation of the presence of high-symmetry electronic bands as well as the utilization of easily produced materials. As the subject of topological insulators is still in the nascent stage, there is growing research and knowledge in the emerging field. This book is intended to provide the readers with an understanding of the needs and application of these materials. Keywords: Topological Insulators, Insulators, One-Dimensional Topological Insulators, Graphene, Magnetic Topological Insulator, Antiferromagnetic Phase, Ferromagnetic Phase, Topological Superconductor, Nonlinear Optical Behavior, Saturable Absorber, Quantum, Band Gap, Photonic Topological Insulators.

Download or read book Topological Insulators written by Frank Ortmann and published by John Wiley & Sons. This book was released on 2015-04-07 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: There are only few discoveries and new technologies in physical sciences that have the potential to dramatically alter and revolutionize our electronic world. Topological insulators are one of them. The present book for the first time provides a full overview and in-depth knowledge about this hot topic in materials science and condensed matter physics. Techniques such as angle-resolved photoemission spectrometry (ARPES), advanced solid-state Nuclear Magnetic Resonance (NMR) or scanning-tunnel microscopy (STM) together with key principles of topological insulators such as spin-locked electronic states, the Dirac point, quantum Hall effects and Majorana fermions are illuminated in individual chapters and are described in a clear and logical form. Written by an international team of experts, many of them directly involved in the very first discovery of topological insulators, the book provides the readers with the knowledge they need to understand the electronic behavior of these unique materials. Being more than a reference work, this book is essential for newcomers and advanced researchers working in the field of topological insulators.

Download or read book Superconductivity in Graphene and Carbon Nanotubes written by Pablo Burset Atienza and published by Springer. This book was released on 2013-10-11 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The unique electronic band structure of graphene gives rise to remarkable properties when in contact with a superconducting electrode. In this thesis two main aspects of these junctions are analyzed: the induced superconducting proximity effect and the non-local transport properties in multi-terminal devices. For this purpose specific models are developed and studied using Green function techniques, which allow us to take into account the detailed microscopic structure of the graphene-superconductor interface. It is shown that these junctions are characterized by the appearance of bound states at subgap energies which are localized at the interface region. Furthermore it is shown that graphene-supercondutor-graphene junctions can be used to favor the splitting of Cooper pairs for the generation of non-locally entangled electron pairs. Finally, using similar techniques the thesis analyzes the transport properties of carbon nanotube devices coupled with superconducting electrodes and in graphene superlattices.

Download or read book Pressure Evolution of Electrical Transport in the 3D Topological Insulator Bi Sb 2 Se Te 3 written by and published by . This book was released on 2014 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advanced Topological Insulators written by Huixia Luo and published by Wiley-Scrivener. This book was released on 2019-04-09 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is the first pedagogical synthesis of the field of topological insulators and superconductors, one of the most exciting areas of research in condensed matter physics. Presenting the latest developments, while providing all the calculations necessary for a self-contained and complete description of the discipline, it is ideal for researchers and graduate students preparing to work in this area, and it will be an essential reference both within and outside the classroom. The book begins with the fundamental description on the topological phases of matter such as one, two- and three-dimensional topological insulators, and methods and tools for topological material's investigations, topological insulators for advanced optoelectronic devices, topological superconductors, saturable absorber and in plasmonic devices. Advanced Topological Insulators provides researchers and graduate students with the physical understanding and mathematical tools needed to embark on research in this rapidly evolving field.

Download or read book Transport Studies of Topological Insulators written by Dongxia Qu and published by . This book was released on 2011 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Topological Insulator and Magnetically Doped Topological Insulator Thin Films by Molecular Beam Epitaxy written by Shuang Li and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Searching for energy dissipation-less systems has become increasingly important for low power electronic devices. Topological insulators, a new topological state of quantum matter, have recently been proposed as an emerging material for use in low power electronics, because of the unique transport along its topologically protected edge/surface states. In addition, it has been predicted that the incorporation of magnetic elements into topological insulators could lead to the quantum anomalous Hall state, which is a truly dissipation-less system. However, the material quality of topological insulator thin films remains as a major stumbling block for exploring the novel physics of topological insulators and their proposed applications. In the first part of this thesis, I will first describe an advanced thin film deposition technique, molecular beam epitaxy (MBE) and the mini-MBE system we designed and built for topological insulator thin film growth. Then I will briefly illustrate some basic principles and sample preparation methods for a variety of characterization techniques we used for the material property investigation. In the second part of this thesis, I will present the growth and characterization of topological insulator bismuth telluride thin films grown by a two-step MBE process developed as part of this research. By optimizing the growth recipe and particularly developing the two-step growth method, defect densities were significantly reduced and higher crystal and surface quality bismuth telluride thin films were achieved. The existence of a topological surface state on our bismuth telluride thin films was also confirmed. The Fermi level of our bismuth telluride thin film was tuned to very close to the bulk gap region. The successful growth of centimeter-sized, uniform, high quality topological insulator thin films provides an excellent platform for both fundamental studies of the properties of topological insulators and fabrications of mesoscopic devices. Finally, I will report on the first successful growth of gadolinium substituted bismuth telluride thin films with high Gd concentrations by MBE. We systematically investigated the crystal structure, band structure, magnetic, and electronic properties of gadolinium substituted bismuth telluride thin films. The topological surface state was found to remain intact by Gd substitution into bismuth telluride. Although ferromagnetic behavior in gadolinium substituted bismuth telluride thin films was not observed above 2K by both magnetic and magneto-transport measurements, gadolinium substituted bismuth telluride thin films were found to have a Curie susceptibility due to the paramagnetic Gd ions with an atomic magnetic moment of 6.93 Bohr magneton per Gd ion, which suggests that it is possible to realize dissipation-less transport with a small external magnetic field or with a ferromagnetic layer on top of gadolinium substituted bismuth telluride thin films.

Download or read book Electronic Transport in Topological Insulator Nanostructures written by Seung Sae Hong and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological insulators are states of quantum matter with an insulating gap in the bulk and gapless surface states. The exotic spin nature of the surface electrons, resulting in topological protection from localization, suggests unconventional applications in electronics as well as fundamental scientific interests. While these exotic states have been investigated via surface-sensitive techniques intensively, electronic transport device, crucial to realize topological electronics, has lagged behind due to material challenges in candidate materials. Topological insulator nanostructure is an attractive candidate for device applications, as the size effect and boundary conditions offer a unique way to enhance / tailor the surface electron transport. In this dissertation, we first describe the design principle of topological insulator nanomaterials, with an emphasis on bismuth selenide. Two major material challenges, dominant bulk electron contribution and low surface mobility due to surface oxidation, are discussed and the solutions via nanomaterial synthesis are achieved. Elemental doping and core-shell heterostructures are developed to suppress bulk carriers and to achieve high surface electron mobility. The high electronic mobility allows us to observe Shubnikov-de Haas oscillations originated from the surface Dirac fermions. In addition to the material development, we also investigate transport properties from helical nature of the surface electrons. 1D modes of surface electrons in bismuth selenide nanowire Aharonov-Bohm interferometers is a unique electronic state providing an opportunity to reveal helical spin nature and topological protection via transport. The helical 1D mode, directly observed near the Dirac point under half magnetic flux quantum, is robust against disorder but fragile against a magnetic field breaking time-reversal-symmetry. The newly discovered 1D helical mode is expected to open a new direction to study topological electronics, as well as future applications.

Download or read book Transport Properties and Electrical Field Effect Study of Topological Insulator Bi Sb 2Te3 Magnetic Insulator EuIG Heterostructures written by Wei-Jhih Zou and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Lietuvos kio paskutinis de imtmetis written by and published by . This book was released on 1938 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Topological Insulators written by Vadim Nemytov and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "In this thesis we investigate quantum transport properties of topological insulator (TI) Bi2 Se3 from atomistic point of view. TI is a material having an energy gap in its bulk but supporting gapless helical states on its boundary. The helical states have Dirac-like linear energy dispersion continuously crossing the bulk band gap with a spin texture in which the electron spin is locked perpendicular to the electron momentum. The peculiar electronic structure of TI material Bi2 Se3 is due to a strong spin-orbit interaction and is protected by the time reversal symmetry. The thesis consists of two main parts. The first reviews the theory of TI and the second presents our atomistic calculations of electron transport in the Bi2 Se3 material. In the theoretical review of the physics of TI, I follow the literature and attempt to present it in a reasonably accessible manner. The theory of TI is explained in terms of well known physical phenomena including classical and quantum Hall effects, spin-orbit coupling, spin current, and spin-Hall effect. The concept of Berry's phase is then introduced to link with the formal conventionalclassification of TI by the topological Z2 invariants. The entire discussion is within the well known Bloch band theory. In the second part of this thesis, numerical studies of transport properties of Bi2 Se3 are presented. After a brief discussion of the relevant quantum transport theory and the tight binding atomistic model, we present our calculated quantum transport results of Bi2 Se3 films having a trench in the middle. Such a large defect, if on normal conductors, would cause significant back scattering of the carriers. Here, by topological protection of the helical states, back scattering is forbidden due to the spin-momentum locking. Nevertheless, large trenches in the film may cause the helical states on the surface to mix inside the trench, thereby affecting the transmission." --

Download or read book Applications of Laser Ablation written by Dongfang Yang and published by BoD – Books on Demand. This book was released on 2016-12-21 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt: Laser ablation refers to the phenomenon in which a low wavelength and short pulse (ns-fs) duration of laser beam irradiates the surface of a target to induce instant local vaporization of the target material generating a plasma plume consisting of photons, electrons, ions, atoms, molecules, clusters, and liquid or solid particles. This book covers various aspects of using laser ablation phenomenon for material processing including laser ablation applied for the deposition of thin films, for the synthesis of nanomaterials, and for the chemical compositional analysis and surface modification of materials. Through the 18 chapters written by experts from international scientific community, the reader will have access to the most recent research and development findings on laser ablation through original research studies and literature reviews.