Download or read book Electronic and Magnetic Properties of MBE Grown Topological Semimetals written by Timothy Pillsbury and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Exploring and expanding the menagerie of topological materials has been at the forefront of condensed matter physics for over a decade. With the discovery of each new class of materials, starting with graphene, followed by topological insulators, and continuing most recently into topological semimetals, new paradigms have been discovered that provide a platform for exploring fundamental physics as well as novel practical applications. Crucial to all these innovations has been the topologically protected edge and surface states, which in addition to their robust nature, also have strong spin or valley correlation with momentum, offering direct coupling of macroscopic electronic properties to the quantum state of electrons. The interaction between magnetism and topology has lead to novel quantum phenomena, such as the quantum anomalous Hall effect, as well as enhanced device capabilities, such as the switching of magnetic polarization via the topological surface states. In topological semimetals, it is predicted that magnetism creates a transition from a Dirac to a Weyl semimetal phase by breaking time-reversal symmetry. Experimentally realizing such a transition will provide a fundamental platform for examining the emergence of Weyl fermions, as well as a practical platform for engineering tailored Weyl semimetals, including the ideal case of two Weyl nodes which has yet to be discovered in any intrinsic Weyl semimetal. The material system explored most extensively throughout this dissertation is the transition metal dichalcogenide Dirac semimetal ZrTe2. Thus far, a few thin film studies have demonstrated the existence of a Dirac semimetal phase in this material directly through angle resolved photoemission spectroscopy (ARPES) analysis of the Dirac cone as well as through transport measurements of the chiral anomaly. Additionally, a very recent experiment demonstrates the existence of a superconducting phase in ZrTe2 that could lead to further interest if it is shown to coexist with the Dirac semimetal phase. To facilitate further research into this promising material platform, the first portion of this dissertation focuses on the the development of high quality ZrTe2 thin films on insulating substrates. This is a necessary step for characterizing the electronic states of the material as well as adapting it for spintronics. Through transmission electron microscopy, scanning tunneling microscopy, and x-ray diffraction, the lattice structure and quality are assessed. ARPES and transport measurements demonstrate hole-like carriers. While this matches theoretical predictions for this material, it is at odds with most of the current literature, which demonstrates n-type carriers due to the high defect density. To observe the Dirac cone, tellurium vacancies are intentionally introduced for ARPES measurements, although this method was not effective for transport measurements. Ultimately, this prevents the observation of many of the desirable transport phenomena expected of a Dirac semimetal. Finally, we report the presence of weak anti-localization in ZrTe2 thin films at low temperatures. After establishing the MBE growth of ZrTe2 thin films, chromium dopants are introduced into these films to form (CrxZr1-x)Te2. Structural characterization is consistent with a transition between the Dirac semimetal ZrTe2 and the recently discovered metallic 2D ferromagnet CrTe2. This makes it phenomenologically distinct from a recently reported Cr-intercalated ZrTe2, which did not demonstrate similar changes in lattice structure and demonstrates completely different ARPES and transport phenomena. The (CrxZr1-x)Te2 thin films presented in this work are demonstrated to be ferromagnetic, with a TC of ∼150 K, as revealed via the anomalous Hall effect as well as magnetometry measurements. This system could be a critical component for realizing the transition from a Dirac to a Weyl semimetal, although currently it is limited by the location of the Fermi level. Finally, the next steps to utilizing the Dirac semimetal ZrTe2 in real devices are presented. Additionally, other methods of inducing magnetism based on the foundation laid by the study of (CrxZr1-x)Te2 are explored, such as magnetic proximity effect and alternative dopants. Ultimately, this research presents an approach towards tailoring magnetism in topological semimetals that has important implications for examining the transition between Dirac and Weyl semimetals through time-reversal symmetry breaking as well as for designing functional materials for spintronics applications.

Download or read book Magnetic Metal organic written by Marc González Cuxart and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological Insulators (TIs) have become one of the wonder materials of condensed matter physics over the last decade due to their novel properties, possessing an insulating bulk in coexistence with metallic boundaries. They present an inverted band gap consequence of strong spin orbit coupling, which gives rise to the conductive boundary states with linear dispersion, characteristic of Dirac fermions, and helical spin polarization. Numerous materials have been predicted and observed to have TI signatures, holding great perspective for the realization of novel applications in spintronics, quantum computing and metrology. The experimental realization of three-dimensional TIs with the the Fermi Level located well in the bulk band gap is a challenging task because of their relatively small gap of hundreds of meV, and their high sensibility to crystal defects and impurities. These can induce electron doping that activates bulk conduction channels, thus burying the contribution of the surface states to the transport. Molecular Beam Epitaxy (MBE) has been reported to be the most suitable growth method to overcome this hindrance, due to its capability to grow single crystals with fine control over the crystal defects and impurity level. The first part of this thesis deals with the growth of high-quality TIs that maintain their pristine insulating bulk behaviour. By using MBE, we studied the impact of different substrates and growth parameters to the synthesis of Bismuth Telluride (Bi2Te3) thin films, and the growth of the ternary compound Bismuth-Antimony Telluride. We were able to grow insulating Bi2Te3 thin films with complete suppression of the \twin" domains, mirror-symmetric domains that contribute to the self-doping of the crystal. By a combination of the initial interaction with the lattice-matched Barium Fluoride substrate and the high working temperatures, the growth of Bi2Te3 single-crystalline films is achieved already from the first layer. More importantly, the films present low-doping level with the the Fermi Level kept in the bulk band gap. The correlation between the lack of \twin" domains (measured by Re ection High-Energy Electron Diffraction, X-ray Diffraction and Atomic Force Microscopy) and the low-doping level measured by Angle- Resolved Photoemission Spectroscopy (ARPES), indicates the relation between the crystal quality and the capability to preserve the bulk insulating character. This result contrasts to other TIs grown on more conventional substrates, typically presenting large lattice misfits that lead to the formation of an initial polycrystalilne or amorphous seed layer. In parallel, we explored a complemeniii tary approach to the growth of insulating Bi2Te3, based on the addition of Sb at the expense of Te atoms. A sequence of Bismuth-Antimony Telluride films with different x content were measured by X-ray Photoemission Spectroscopy (XPS) and ARPES, showing that the the Fermi Level can be gradually brought to the bulk valence band. The realization of such TIs, with a controlled level of the the Fermi Level position is of special interest for counteracting the n-doping effects typically induced by the addition of magnetic materials. The second and more extended part of this thesis is devoted to the study of interfaces formed by magnetic Metal-organic molecules deposited on the TI thin films. Interfacing TI surfaces with magnetic materials can give rise to novel magnetoelectronic phenomena, involving the manipulation of spin-torques (Inverse Edelstein Effect), or the realization of spin polarized edge states (Quantum Anomalous Hall Effect). The realization of such spin-related effects rely on the capability to control the interfacial magnetic and electronic interactions. The use of organic molecules to cage magnetic ions has been proved to be a versatile approach to engineer inter-ions and ions-surface interactions, due to the exible design that molecules offer and to their ability to form structurally perfect selfassembled structures. Moreover, they can also act as building blocks for covalent or coordination structures via on-surface reactions. As a first approach to tune the interfacial properties with Metal-organic molecules, we showed how the ligand chemistry allows a progressive control over the magnetic interactions between a hosted Co ion and a prototypical Au surface. The spin states and magnetic moments are comprehensively studied thanks to the complementary use of local spectroscopic Scanning Tunneling Spectroscopy and non-local magnetic sensitive X-ray Magnetic Circular Dichroism (XMCD) techniques, which are supported theoretically by Density Functional Theory (DFT). We were able to continuously cover the range of magnetic Co ion-substrate interactions, from a strong interacting scenario where the magnetic moment is quenched, to a gradual decrease of the interaction revealed by a lower Kondo screening of the spin. In addition, by changing the Au surface for a TI surface, the interfacial interactions reach the weakest limit in which the molecular magnetic structure is completely decoupled from the substrate electrons. Thereafter, we explored the electronic and magnetic interactions between the Topological Surface State of the Bi2Te3 thin film and Co ions caged in two different planar molecules such as Cobalt - Tetrakis (4-Promophenyl) Porphyrin (CoTBrPP) and Cobalt - Phthalocyanine (CoPc). We found a Metal-organic / TI interface with unperturbed electronic and magnetic properties. This is assessed by a coverage dependent ARPES study in which the Topological Surface State persists upon the deposition of one (CoTBrPP or CoPc) molecular layer. On the other hand, XMCD and Scanning Tunneling Spectroscopy measurements reveal the preservation of the pristine CoTBrPP magnetic moment and electronic structure respectively. Furthermore, a comprehensive Scanning Tunneling Microscopy (STM) and DFT study of the CoTBrPP adsorption geometry describes weak molecule-surface interactions, and corroborates the electronic decoupling of the Metal-organic layer from the TI surface. In an analogue study with CoPc we find slightly stronger interactions yet within the non-perturbative regime, that suggesting ligand chemistry can be used to tune magnetic interactions without affecting the overall properties of each component of the heterostructure. Subsequently, the Br-functionalized CoTBrPP on Bi2Te3 system was used to induce on-surface synthesis of Metal-organic coordination networks on TI. These more entangled structures are of great interest as a framework in which magnetic ions could arrange in ordered and mechanically stable arrays. Two different coordination phases are selectively created after CoTBrPP dehalogenation upon thermal activation. We track the chemical reaction by XPS, and investigate the morphological and electronic properties of the final products by combining Scanning Tunneling Spectroscopy (STS) and DFT calculations. We conclude that the resulting structures consists of CoTPP coordinated with Te atoms incorporated from the substrate, and thanks to the supporting DFT calculations, we are able to explain the presence of linear chains and irregular coordinated networks. In parallel, the presence of unperturbed Topological Surface State upon the formation of the Metal-organic structures is confirmed by a coverage-dependent ARPES study. Overall, the first part of the thesis constitutes an extensive study of MBE grown of Bi2Te3 thin films, in which different substrates and growth conditions are discussed. Furthermore, the results provide a route for the enhancement of the crystal quality of simple diatomic TIs, crucial for the preservation of their bulk insulating behaviour. The results presented in the second part conceive the capabilities of organic molecules to tune magnetic interactions between Co atoms and Bi2Te3 films, and pave the way for the on-TI surface synthesis of magnetic supramolecular structures.

Download or read book Topological Semimetals written by David J. Fisher and published by Materials Research Forum LLC. This book was released on 2019-04-20 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological semimetals are quantum materials that are not only extremely interesting from a theoretical point of view but also have a great potential for technological applications in which superconducting, semiconducting and other semimetal behaviors are involved. Keywords: Quantum Materials, Macroscopic Quantum Phenomena, Topological Semimetals, Dirac Semimetals, Weyl Semimetals, Nodal-Line Semimetals, Antimony and Antimonides, Antimonene, Arsenides, Bismuthides, Boron, Borides, Borophene, Carbon and Carbides, Chalcogenides, Nitrides, Phosphorus, Phosphides, Silicides, Topological Metals, Topological States of Matter.

Download or read book Linear Electrodynamic Response of Topological Semimetals written by Artem V. Pronin and published by Springer Nature. This book was released on 2023-08-17 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a model description for the electromagnetic response of topological nodal semimetals and summarizes recent experimental findings in these systems. Specifically, it discusses various types of topological semimetals – Dirac, Weyl, nodal-line, triple-point, and multifold semimetals – and provides description for the characteristic features of the linear electrodynamic response for all these types of materials. Topological semimetals possess peculiar bulk electronic band structure, which leads to unusual electrodynamic response. For example, the low-energy inter-band optical conductivity of nodal semimetals is supposed to demonstrate power-law frequency dependence and the intra- and inter-band contributions to the conductivity are often mixed. Further, the magneto-optical response is also unusual, because of the non-equidistant spacing between the Landau levels. Finally, in semimetals with chiral electronic bands, e.g. in Weyl semimetals, the simultaneous application of parallel magnetic and electric fields leads to the chiral anomaly, i.e. to a misbalance between the electrons with diffident chiralities. This misbalance affects the electrodynamics properties of the material and can be detected optically. All these points are addressed here in detail. The book is written for a wide audience of physicists, working in the field of topological condensed matter physics. It gives a pedagogical introduction enabling graduate students and non-experts to familiarize themselves with the subject.

Download or read book Two Dimensional Ferromagnetism and Topology at the Surface of MnBi 2 Te 4 Bi 2 Te 3 Heterostructures written by Philipp Thomas Kagerer and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation of Electronic and Magnetic Responses in Topological Semimetals written by Sukriti Singh and published by . This book was released on 2022* with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book MBE Growth and Spin Injection Measurements of Ferromagnetic Alloy Nickel manganese indium on III V Semiconductors written by Junqing Xie and published by . This book was released on 2005 with total page 312 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Molecular Beam Epitaxy written by Mohamed Henini and published by Elsevier. This book was released on 2018-06-27 with total page 790 pages. Available in PDF, EPUB and Kindle. Book excerpt: Molecular Beam Epitaxy (MBE): From Research to Mass Production, Second Edition, provides a comprehensive overview of the latest MBE research and applications in epitaxial growth, along with a detailed discussion and 'how to' on processing molecular or atomic beams that occur on the surface of a heated crystalline substrate in a vacuum. The techniques addressed in the book can be deployed wherever precise thin-film devices with enhanced and unique properties for computing, optics or photonics are required. It includes new semiconductor materials, new device structures that are commercially available, and many that are at the advanced research stage. This second edition covers the advances made by MBE, both in research and in the mass production of electronic and optoelectronic devices. Enhancements include new chapters on MBE growth of 2D materials, Si-Ge materials, AIN and GaN materials, and hybrid ferromagnet and semiconductor structures. - Condenses the fundamental science of MBE into a modern reference, speeding up literature review - Discusses new materials, novel applications and new device structures, grounding current commercial applications with modern understanding in industry and research - Includes coverage of MBE as mass production epitaxial technology and how it enhances processing efficiency and throughput for the semiconductor industry and nanostructured semiconductor materials research community

Download or read book Electronic and Magnetic Properties of Metals and Ceramics written by K. H. J. Buschow and published by . This book was released on 1992 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Tuning Magnetism and Band Topology in Intrinsic Magnetic Topological Insulators MnBi2nTe3n 1 written by Chaowei Hu and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Topological materials are materials whose electronic band structures are described by certain non-trivial topological invariants. Forty years ago the importance of band topology in condensed matter physics was first recognized when the quantum Hall effect (QHE) was found to be related with the integer Chern number in two-dimensional (2D) electron gas. Since 2008, the discovery of three-dimensional (3D) topological insulators (TI) with a non-trivial topological invariant and gapless surface state has taken the field into a new era. Various new topological phases were proposed and band topology has become a new way to classify the state of matter. The design, synthesis and characterization of new topological materials pave essential basis to uncovering novel physics arising from non-trivial band topology and its interplay with various degrees of freedom such as spin, orbital and charge. Today, with more sought-after novel topological phases, emergent phenomena such as surface Fermi arcs, chiral anomaly, quantum anomalous Hall effect were discovered and enable future technological advances including topological quantum computation. A new topological phase can be created when additional symmetry breaking is introduced into an existing topological phase. For example, by breaking the time reversal symmetry of a 3D TI through ferromagnetism (FM), one can get a Chern insulator in its 2D limit, where QHE can be realized without external magnetic field and gives topologically-protected dissipationless chiral edge states. This phenomenon, the so-called quantum anomalous Hall effect (QAHE), has been long sought since its early proposal in the yet-to-be-realized Haldane model for graphene lattice with opposite magnetic field at neighboring atoms in 1988. Therefore, the realization of QAHE in magnetically-doped TI Cr0.15(Bi0.1Sb0.9)1.85Te3 thin films in 2013 was revolutionary. However, the unavoidable sample inhomogeneity in doped materials restrains the investigation of associated emergent phenomena in mK-regime. Ideally, magnetism from intrinsic magnetic atoms in a crystal can provide more homogeneous electronic and magnetic properties than the magnetism from dopants. To realize QAHE at higher temperatures, the intrinsic magnetic TIs with only clean topological bands but no other bands at the Fermi level are strongly desired. In 2018, MnBi2Te4 was discovered to be the first of such kinds, as an antiferromagnetic (AFM) TI with intrinsic magnetic Mn site. It is a layered van der Waals (vdW) material. When the magnetism orders below 24 K, the spins are FM aligned in the ab plane but AFM coupled along the c axis. In 2D limit, MnBi2Te4 films can have a net magnetization either in odd-layer devices, or when the even-layer devices are in the spin-flop state above ~ 3.5 T and the forced FM state above ~ 8 T. These time-reversal-symmetry breaking states are ideal for realizing the Chern insulator state. Indeed, QAHE was experimentally observed at 0 T and 1.6 K in a 5-layer device and quantized Hall conductance was realized when the even-layer devices enter the forced FM state above the saturation field of 8 T. Following this line, for QAHE to be realized at zero field and higher temperature, it is strongly desirable if the FM alignment of Mn spins can be accessed at a lower or even zero field. To do so, one must weaken the interlayer AFM interactions between [MnBi2Te4] layers. We thus propose to introduce n-1 nonmagnetic TI [Bi2Te3] layers between [MnBi2Te4] layers to get natural heterostructures of MnBi2nTe3n+1. By this rational design, we can increase the distance between the neighboring [MnBi2Te4] layers and thus reduce the interlayer AFM interaction. Under such a design principle we successfully grew single crystals of MnBi4Te7 (n=2), MnBi6Te10 (n=3) and MnBi8Te13 (n=4). Then with the physical property characterization, first-principles calculations and angle-resolved photoemission spectroscopy measurements, for the first time, we demonstrated that MnBi4Te7 is an intrinsic AFM TI with saturation field 40 times smaller than that of MnBi2Te4, and that MnBi8Te13 is the first realization of an intrinsic FM axion insulator, proving the success of our material design principle. The manipulation of magnetism is crucial to access different magnetic topological phase and novel physics. In MnBi2nTe3n+1, the control of the magnetism from AFM to FM by n is only discrete. To achieve a fine and continuous control of the magnetic transition, we doped Sb to MnBi4Te7 where the interlayer AFM coupling is weak and more tunable. Through single crystal growth, transport, thermodynamic, neutron diffraction measurements, we show that under Sb doping, MnBi4Te7 evolves from AFM to FM and then ferrimagnetic. We attribute this to the formation of Mn_(Bi, Sb) antisites upon doping, which results in additional Mn sublattices that modify the delicate interlayer magnetic interactions and changes the overall magnetism. We further investigate the effect of antisites on the band topology using the first-principles calculations. Without considering antisites, the series evolves from AFM topological insulator (x = 0) to FM axion insulators. In the exaggerated case of 16.7\% of periodic antisites, the band topology is modified and type-I magnetic Weyl semimetal phase can be realized at intermediate doping. Therefore, this doping series provides a fruitful platform with rich and continuously tunable magnetism and topology. After we achieve FM in MnBi2nTe3n+1, for practical applications especially in the pursuit of high temperature QAHE when fluctuations become important, the study on magnetic dynamics is indispensable too. We investigated the magnetic dynamics in FM MnBi8Te13 and Sb doped MnBi4Te7 and MnBi6Te10 using AC susceptibility and magneto-optical imaging. Slow relaxation behavior is observed in all three compounds, suggesting its universality among FM MnBi2nTe3n+1. The origin of the relaxation behavior is attributed to the irreversible domain movements since they only appear below the saturation fields when FM domains form and evolve. These FM domains are very soft, as revealed by the low-field fine-structured domains and high-field sea-urchin-shaped remnant-state domains imaged via the magneto-optical measurements. Finally, we attribute the rare "double-peak" behavior observed in the AC susceptibility under small DC bias fields to the very soft FM domain formations. This study provides a thorough understanding of the soft FM in highly anisotropic magnets. As the first intrinsic antiferromagnetic topological insulator, MnBi2Te4 is still the major material platform to search for QAHE, so its material optimization is very urged. We develop the chemical-vapor-transport (CVT) growth for of MnBi2Te4, which has a higher success rate in observation of the field-induced quantized Hall conductance in 6-layer devices. Through comparative studies between our CVT-grown and flux-grown MnBi2Te4, we find that CVT-grown MnBi2Te4 is marked with higher Mn occupancy on the Mn site, slightly higher Mn_Bi antisites and smaller carrier concentration. On the device end, thin film from CVT-grown sample shows by far the highest mobility of 2500 cm2 V s in MnBi2Te4 devices with the quantized Hall conductance appearing at 1.8 K and 8 T. This study provides a route to obtain high-quality single crystals of MnBi2Te4 that are promising to make superior devices and realize emergent phenomena. In summary, we have discovered and established MnBi4Te7 and MnBi8Te13 as new intrinsic magnetic topological insulators. In particular, we provide deep understanding of the importance of material design, synthesis and chemical doping to the magnetism and topology in the series. The growths of high-quality single crystals and the study of magnetic dynamics provide essential basis for the search of QAHE in MnBi2nTe3n+1. Our works will shed light on future endeavors in finding novel magnetic topological materials as well as searching for QAHE and the associated emergent phenomena in the condensed matter field

Download or read book Epitaxy Magnetic Doping and the Electronic Structure of Semiconducting Half heusler Fevsb written by Estiaque Haidar Shourov and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heuslers are an attractive multifunctional material family with a wide range of properties. These properties include semiconductivity, half metallic ferromagnetism, superconductivity and topological insulator. Harnessing these properties in real devices require synthesizing high quality epitaxial single crystalline films on suitable substrates. Experimental realization of these properties also warrants a fundamental understanding of the electronic structure. For example, half-Heuslers with predicted band gaps on the order of 0.5 eV often exhibits metallic character which can be understood by the role of the defect states near the Fermi level. To this end, in this work I deploy molecular beam epitaxy (MBE) in combination with angle-resolved photoemission spectroscopy (ARPES) and magnetotransport characterization to synthesize and optimize high quality thin films and to engineer artificial heterostructures based on the half-Heusler compound FeVSb for both improved technological application and the discovery of new physics. I first demonstrate the epitaxial synthesis of the semiconducting half-Heusler FeVSb. I then establish the existence and experimentally mapthe bounds of a semi adsorption-controlled MBE growth window. Due to the high volatility of Sb, the Sb stoichiometry is self-limiting for a finite range of growth temperatures and Sb fluxes, similar to the growth of III-Vsemiconductors such as GaSb and GaAs. Films grown within this window are structurally and compositionally nearly indistinguishable. Leveraging the high crystalline quality of the films, I next measured the electronic structure of FeVSb. ARPES reveals a mass renormalization of m*/m_{bare} = 1.4, where m* is the measured effective mass and m_{bare} isthe mass from density functional theory (DFT) calculations with no added on-site Coulomb repulsion. This measurement is then quantitatively reproduced using dynamical mean field theory (DMFT) calculations, confirming the many-body origin of the mass renormalization. This mass renormalization lies in dramatic contrast to other filled shell intermetallics such as CoTiSb; and has a similar origin to that in FeSi, where Hund's coupling induced fluctuations across the gap can explain a dynamical self-energy and correlations. This finding establishes FeVSb as a novel correlated band insulator. A final result presented here is the synthesis of Fe off-stoichiometric Fe_{1+x}VSb films. For dilute excess Fe (x 0.1), there is a decrease in the Hall electron concentration and no secondary phases in X-ray diffraction (XRD), consistent with Fe doping into FeVSb. Hysteresis in magnetoresistance suggests weak ferromagnetism that onsets at a temperature of T_{c} ~ 5K. For higher Fe content (x 0.1), ferromagnetic Fe nanostructures precipitate from the semiconducting FeVSb matrix. The Fe/FeVSb interfaces are epitaxial, as observed by transmission electron microscopy and XRD. Magnetotransport measurements suggest proximity-induced magnetism in the FeVSb, from the Fe/FeVSb interfaces, at an onset temperature of T_{c} ~ 20K. These three key results demonstrated in the case of a model system FeVSb are fundamental, and can be extended in understanding and realizing a wider range of half-Heusler compounds.

Download or read book Microstructural and Magnetic Properties of Multilayers Grown by Molecular Beam Epitaxy written by Chung-Jen Chien and published by . This book was released on 1992 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterization and Synthesis of BiSb Thin Films written by Yu Sheng Huang and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Bi1-xSbx alloy has garnered significant attention in the fields of semimetals and narrow bandgap semiconductors due to its unique properties in temperature and magnetic fields. The presence of topological surface states in bulk single crystals of the Bi1-xSbx alloy has sparked interest in exploring its potential for spin-orbit-torque (SOT) devices. Thin films of Bi1-xSbx exhibit high electrical conductivity, making them promising candidates for energy-efficient SOT devices. Previous studies have reported remarkable spin Hall angles and magnetization switching at ultralow current densities in Bi1-xSbx films interfaced with metallic ferromagnets, as well as giant unidirectional spin Hall magnetoresistance when interfaced with ferromagnetic semiconductors. These exciting findings have motivated further investigation into the growth of high-quality, single-crystal Bi1-xSbx films using molecular beam epitaxy (MBE) on various substrates. In this dissertation, we present a systematic study of epitaxial Bi1-xSbx thin films grown on (0001) sapphire substrates using MBE, incorporating a thin (Bi0.95,Sb0.05)2Te3 buffer layer. Various characterization techniques, including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), electrical transport, and Raman spectroscopy, were employed to investigate the microscopic structure, quality, and composition of the films. Raman spectroscopy provided valuable insights into the influence of strain on the phonon modes within the thin films. Our results demonstrate the successful growth of epitaxial Bi1-xSbx films with a well-defined growth direction, a crucial aspect for achieving high spin Hall angles in SOT devices. Furthermore, this dissertation emphasizes the effectiveness of characterization techniques for thin films, with a particular focus on XRD pole figure scans. Addressing the lack of standardized documentation in pole figure measurements, we present a clear and consistent approach, contributing to the development of a more standardized methodology in this area. To illustrate the capabilities of pole figure scans, analysis results from our own samples are presented. By comparing peak locations between the sample and substrate, we could assess the quality of epitaxial growth. Moreover, we suggest the potential for qualitative analysis of sample quality through pole figure measurements by examining the full width at half maximum (FWHM) values obtained from azimuthal scans at the maximum intensity, which may provide further insights into sample characteristics. Additionally, this dissertation provides an in-depth overview of two other characterization methods: XPS and Raman spectroscopy. XPS enables accurate analysis of elemental composition, oxidation states, and element migration in thin films. Precise determination of the composition ratio of Bi-Sb thin films using XPS measurements allows for adjustments in the growth process to enhance film quality. Raman spectroscopy, on the other hand, offers insights into bonding, crystal structure, contamination, strain, and material composition. By utilizing these complementary characterization techniques, a comprehensive understanding of Bi1-xSbx thin films can be achieved. Further investigations, such as detailed comparisons with Raman spectroscopy or the utilization of pole figure measurements, have the potential to enable the quantified reporting of strains and other challenging-to-measure information in thin film samples.

Download or read book Exploration of Quantum Transport Phenomena via Engineering Emergent Magnetic Fields in Topological Magnets written by Yukako Fujishiro and published by Springer. This book was released on 2022-12-03 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book addresses novel electronic and thermoelectronic properties arising from topological spin textures as well as topologically non-trivial electronic structures. In particular, it focuses on a unique topological spin texture, i.e., spin hedgehog lattice, emerging in a chiral magnet and explore its novel properties which are distinct from the conventional skyrmion lattice, and discusses the possibility of realizing high-temperature quantum anomalous Hall effect through quantum confinement effect in topological semimetal. This book benefits students and researchers working in the field of condensed matter physics, through providing comprehensive understanding of the current status and the outlook in the field of topological magnets.

Download or read book Topology And Physics written by Chen Ning Yang and published by World Scientific. This book was released on 2019-01-09 with total page 231 pages. Available in PDF, EPUB and Kindle. Book excerpt: 'The book is an engaging and influential collection of significant contributions from an assembly of world expert leaders and pioneers from different fields, working at the interface between topology and physics or applications of topology to physical systems … The book explores many interesting and novel topics that lie at the intersection between gravity, quantum fields, condensed matter, physical cosmology and topology … A rich, well-organized, and comprehensive overview of remarkable and insightful connections between physics and topology is here made available to the physics reader.'Contemporary PhysicsSince its birth in Poincaré's seminal 1894 'Analysis Situs', topology has become a cornerstone of mathematics. As with all beautiful mathematical concepts, topology inevitably — resonating with that Wignerian principle of the effectiveness of mathematics in the natural sciences — finds its prominent role in physics. From Chern-Simons theory to topological quantum field theory, from knot invariants to Calabi-Yau compactification in string theory, from spacetime topology in cosmology to the recent Nobel Prize winning work on topological insulators, the interactions between topology and physics have been a triumph over the past few decades.In this eponymous volume, we are honoured to have contributions from an assembly of grand masters of the field, guiding us with their world-renowned expertise on the subject of the interplay between 'Topology' and 'Physics'. Beginning with a preface by Chen Ning Yang on his recollections of the early days, we proceed to a novel view of nuclei from the perspective of complex geometry by Sir Michael Atiyah and Nick Manton, followed by an entrée toward recent developments in two-dimensional gravity and intersection theory on the moduli space of Riemann surfaces by Robbert Dijkgraaf and Edward Witten; a study of Majorana fermions and relations to the Braid group by Louis H Kauffman; a pioneering investigation on arithmetic gauge theory by Minhyong Kim; an anecdote-enriched review of singularity theorems in black-hole physics by Sir Roger Penrose; an adventure beyond anyons by Zhenghan Wang; an aperçu on topological insulators from first-principle calculations by Haijun Zhang and Shou-Cheng Zhang; finishing with synopsis on quantum information theory as one of the four revolutions in physics and the second quantum revolution by Xiao-Gang Wen. We hope that this book will serve to inspire the research community.

Download or read book Inorganic and Organic Thin Films written by Yu Song and published by John Wiley & Sons. This book was released on 2021-07-19 with total page 771 pages. Available in PDF, EPUB and Kindle. Book excerpt: Learn more about foundational and advanced topics in polymer thin films and coatings besides species with this powerful two-volume resource The two-volume Inorganic and Organic Thin Films: Fundamentals, Fabrication, and Applications delivers a foundational resource for current researchers and commercial users involved in the design and fabrication of thin films. The book offers newcomers to the field a thorough description of new design theory, fabrication methods, and applications of advanced thin films. Readers will discover the physics and chemistry underlying the manufacture of new thin films and coatings in this leading new resource that promises to become a handbook for future applications of the technology. This one-stop reference brings together all important aspects of inorganic and polymeric thin films and coatings, including construction, assembly, deposition, functionality, patterning, and characterization. Explorations of their applications in industries as diverse as information technology, new energy, biomedical engineering, aerospace, and oceanographic engineering round out this fulsome exploration of one of the most exciting and rapidly developing areas of scientific and industrial research today. Readers will also learn from: A comprehensive introduction to the progress of thin films and coatings as well as fundamentals in functional thin films and coatings An exploration of multi-layered magnetic thin films for electron transport control and signal sensing, including giant magnetoresistance, colossal magnetoresistance, tunneling magnetoresistance, and the quantum anomalous Holzer effect An in time summary of high-quality magneto-optics, nanophotonics, spin waves and spintronics using bismuth-substituted iron garnet thin films as examples A thorough discussion of template-assisted fabrication of nanostructure thin films for ultrasensitive detection of chemicals and biomolecules A treatment of biomass derived functional films and coatings Perfect for materials scientists and inorganic chemists, Inorganic and Organic Thin Films will also earn a place in the libraries of solid state physicists and physical chemists working in private industry, as well as polymer and surface chemists who seek to improve their understanding of thin films and coatings.

Download or read book Advanced Topological Insulators written by Huixia Luo and published by John Wiley & Sons. This book was released on 2019-03-12 with total page 420 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.