An Investigation of Materials at the Intersection of Topology and Magnetism Using Scanning Tunneling Microscopy PDF Download
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Author: Robert Conner Walko
Publisher:
ISBN:
Category : Condensed matter
Languages : en
Pages : 0
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Book Description
Material systems that combine magnetism and topology have garnered intense interest recently due to predictions of a variety of phenomena such as the quantum anomalous Hall effect, chiral topological edge states, magnetoelectric effects, and Weyl semimetal and axion insulator phases. In this dissertation scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) are used to investigate the structural and electronic properties of several materials that exist at the intersection of topology and magnetism such as topological insulators, van der Waals layered materials, two-dimensional magnets, and intrinsic magnetic topological insulators. Specifically, STM was used to confirm the growth quality and properties of thin films grown by molecular beam epitaxy including Bi2Se3, SnSe2, MnSe, and Fe3GeTe2. In the van der Waals heterostructure SnSe2/Bi2Se3 a moiré pattern was observed which was found to be correlated to a set of localized electronic states in STS measurements. STM was also used to provide feedback for the growth of the heterostructure MnSe/Bi2Se3, which led to successful growth of partial monolayers of MnSe. In Fe3GeTe2, a magnetic field dependent Kondo lattice behavior was observed as well as a ferromagnetic hysteresis loop using spin-polarized STM. In addition, this work reports the first STM study of the recently experimentally verified intrinsic antiferromagnetic topological insulator (AFM TI) MnBi2Se4. Its atomic and layered properties are found to reasonably match theoretical predictions. Two different terminations of its layered structure are observed on the surface with distinct electronic properties. In-gap states are observed near some step edges which could be related to predicted topological edge states. Another AFM TI, the related material MnBi2Te4, was also studied in which nanoscale surface manipulation using an STM tip was demonstrated.
Author: Robert Conner Walko
Publisher:
ISBN:
Category : Condensed matter
Languages : en
Pages : 0
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Book Description
Material systems that combine magnetism and topology have garnered intense interest recently due to predictions of a variety of phenomena such as the quantum anomalous Hall effect, chiral topological edge states, magnetoelectric effects, and Weyl semimetal and axion insulator phases. In this dissertation scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) are used to investigate the structural and electronic properties of several materials that exist at the intersection of topology and magnetism such as topological insulators, van der Waals layered materials, two-dimensional magnets, and intrinsic magnetic topological insulators. Specifically, STM was used to confirm the growth quality and properties of thin films grown by molecular beam epitaxy including Bi2Se3, SnSe2, MnSe, and Fe3GeTe2. In the van der Waals heterostructure SnSe2/Bi2Se3 a moiré pattern was observed which was found to be correlated to a set of localized electronic states in STS measurements. STM was also used to provide feedback for the growth of the heterostructure MnSe/Bi2Se3, which led to successful growth of partial monolayers of MnSe. In Fe3GeTe2, a magnetic field dependent Kondo lattice behavior was observed as well as a ferromagnetic hysteresis loop using spin-polarized STM. In addition, this work reports the first STM study of the recently experimentally verified intrinsic antiferromagnetic topological insulator (AFM TI) MnBi2Se4. Its atomic and layered properties are found to reasonably match theoretical predictions. Two different terminations of its layered structure are observed on the surface with distinct electronic properties. In-gap states are observed near some step edges which could be related to predicted topological edge states. Another AFM TI, the related material MnBi2Te4, was also studied in which nanoscale surface manipulation using an STM tip was demonstrated.
Author: Jacob John Repicky
Publisher:
ISBN:
Category : Magnetism
Languages : en
Pages : 0
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Book Description
As conventional electronics approach the physical limits of size and speed, desire for more capable and energy efficient technologies has driven studies of the individual and collective behavior of electron spins within solid state materials to achieve new forms of information processing. Recent developments in this field of spintronics have led to the discovery particle-like magnetic textures called magnetic skyrmions where spins are arranged in a swirling, vortex-like pattern. To advance the understanding of materials capable of stabilizing magnetic skyrmions and the mechanisms that govern their stability and dynamical properties, we use spin-polarized scanning tunneling microscopy. The research presented here builds on the connection between the physical and magnetic structure at the surface of materials. First, we observe novel surface structures and investigate the electronic and magnetic properties of Cr(001) and Fe/Ir(111), two systems that can be used to characterize the magnetic tip of the scanning tunneling microscope. Next, we detail a technique to determine the grain structure of B20-type magnetic materials FeGe and MnGe, where the structural chirality is known to determine the chirality of the magnetic textures. The surface termination, stacking order of the layered atomic lattice, and grain chirality can all be identified by analysis of the atomic corrugation and insights from density functional theory calculations. Finally, we observe novel topological spin textures at the surface of MnGe(111). The stabilization of these is correlated to structural deformation of the film, and their three-dimensional structure is deduced based on comparison of the spin-polarized imaging with micromagnetic simulations.
Author: Roland Wiesendanger
Publisher: Springer Science & Business Media
ISBN: 3642793665
Category : Science
Languages : en
Pages : 359
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Book Description
Scanning Tunneling Microscopy II, like its predecessor, presents detailed and comprehensive accounts of the basic principles and the broad range of applications of STM and related scanning probe techniques. The applications discussed in this volume come predominantly from the fields of electrochemistry and biology. In contrast to those in STM I, these studies may be performed in air and in liquids. The extensions of the basic technique to map other interactions are described in chapters on scanning force microscopy, magnetic force microscopy, and scanning near-field optical microscopy, together with a survey of other related techniques. Also discussed here is the use of a scanning proximal probe for surface modification. Together, the two volumes give a comprehensive account of experimental aspects of STM and provide essential reading and reference material. In this second edition the text has been updated and new methods are discussed.
Author: Peter, Moritz
Publisher: KIT Scientific Publishing
ISBN: 3731504103
Category : Physics
Languages : en
Pages : 164
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Book Description
The present work introduces a new concept for magnetic resonance measurements in the GHz regime inside a scanning tunneling microscope. It is based on heterodyne detection in a spin-polarized tunneling barrier. The experimental requirements, including a new method to suppress transmission effects, are explained. Measurements on three model systems which were studied to validate the new technique are presented and compared to simulations.
Author: Michael Gottschalk
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 0
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Topological phases in condensed matter systems have received tremendous interest in the past two decades. Theoretical work has shown how topological invariants can be calculated from the band structures in a wide range of insulating systems that contain an energy gap. Broadly speaking, these topological invariants are quantities that are invariant under continuous deformation so long as specific symmetries hold and the energy gap stays open. What separates topological states of matter from traditional phases is the concept of bulk-boundary correspondence. The topology of the vacuum is trivial, so if the bulk of a material is topologically non-trivial, the energy gap must close at the boundary between the two. This creates conducting states at the boundaries, or edges, of the material; the conducting states within the gap have specific properties. Strong, 3Dtopological insulators, such as Bi2Se3 , are materials that are insulating in the bulk with conducting surface states due to bulk-boundary correspondence. The surface states are topologically protected from local perturbations and feature a linear dispersion relation, known as the Dirac cone. Bi2Se3is one of the most widely studied topological insulators due to the relative simplicity of its band structure with a single Dirac cone. In this work, I study the effects of N2 gas on the surface states of Bi2Se3 , which appears to p-type dope the density of states spectra measured with a scanning tunneling microscope. Topological superconductors have also garnered great interest for their potential applications in topological quantum computing. The second half of this dissertation is focused on describing, fabricating, and measuring a potential platform for a possible topological superconducting state known as a Majorana zero mode. These devices feature Nb sputtered onBi2Se3 that is patterned into Josephson junctions with e-beam lithography techniques.
Author:
Publisher: Academic Press
ISBN: 008086015X
Category : Science
Languages : en
Pages : 481
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Book Description
Scanning tunneling microscopy (STM) and its extensions have become revolutionary tools in the fields of physics, materials science, chemistry, and biology. These new microscopies have evolved from their beginnings asresearch aids to their current use as commercial tools in the laboratory and on the factory floor. New wonders continue to unfold as STM delivers atomic scale imaging and electrical characterization of the newly emerging nanometer world. This volume in the METHODS OF EXPERIMENTAL PHYSICS Series describes the basics of scanning tunneling microscopy, provides a fundamental theoretical understanding of the technique and a thorough description of the instrumentation, and examines numerous examples and applications. Written by the pioneers of the field, this volume is an essential handbook for researchers and users of STM, as well as a valuable resource for libraries.
Author: 張昱
Publisher:
ISBN:
Category : Scanning tunneling microscopy
Languages : en
Pages : 0
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Author: Michael Bowker
Publisher: Wiley-VCH
ISBN: 3527628835
Category : Science
Languages : en
Pages : 270
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Book Description
Here, top international authors in the field of STM and surface science present first-class contributions on this hot topic, bringing the reader up to date with the latest developments in this rapidly advancing field. The focus is on the nanoscale, particularly in relation to catalysis, involving developments in our understanding of the nature of the surfaces of oxides and nanoparticulate materials, as well as adsorption, and includes in-situ studies of catalysis on such model materials. Of high interest to practitioners of surface science, nanoscience, STM and catalysis.
Author: Kane Lee Scipioni
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Xinzhou Tan
Publisher:
ISBN:
Category :
Languages : en
Pages : 156
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Book Description
The first part of this dissertation introduces the theoretical background for the Magnetic Force Microscope (MFM), the Spin Polarized Scanning Tunneling Microscope (SP-STM), and the theoretical basis for magnetic domains.The second part addresses issues on the design and construction of a low temperature magnetic force microscope (LT-MFM) and its operation. The third part focuses on the LT-MFM experimental investigation on ternary UMn2Ge2 crystals. The forth part describes the construction and implementation of a low temperature SP-STM system. Scanning probe microscopy (SPM), beginning with the invention of the STM, was first developed to study the electronic properties of different materials, such as imaging high T[subscript c] superconductors. But soon, as the SPM family expanded, some of them developed into powerful techniques to characterize magnetic features. This category includes MFM and SP-STM. The former was widely used for imaging surface magnetic properties from hundreds of micrometers down to the nanometer scale, ideal for imaging magnetic domains. With our homemade LT-MFM system, we studied UMn2Ge2 single crystals, in which both the Uranium and Manganese atoms are magnetic. Flower-like magnetic domain pattern were found at room temperature, and they persisted all the way down to low temperature. Around 150K, Uranium atom ordering was revealed in the form of magnetic domain wall jumps, by partially saturating the sample and warming it up in zero field. In addition, the underlying mechanism of the flower pattern was explained using the domain branching scheme. On the other hand, a Low temperature SP-STM (LT-SP-STM) was designed and constructed, paving the way for spin mapping at the atomic scale thus characterizing magnetic materials with ultra-resolution.
