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Author: Shyama Varier Ramankutty Publisher: ISBN: 9789462339323 Category : Languages : en Pages : 151
Book Description
"Quantum materials pack the spooky properties of quantum mechanics into real-life materials you can make, pick up with tweezers and study in the lab. Those of interest to us show special electronic properties of great fundamental interest and have applications potential for future computer and electronics technologies. This thesis studies quantum materials in which the electronic states possess a special kind of twist, giving them a different topology to their regular electronic material cousins. Picturing the difference between a Möbius strip and a regular loop helps us get the idea of objects with differing topology. The research presented investigates the electronic states directly, using the photoelectric effect in angle resolved photoemission spectroscopy (ARPES) experiments, and was carried out on the candidate quasi-2D Dirac semimetal - SrMnSb2, a trio of rare earth hexaboride compounds, namely SmB6, YbB6 and CeB6, and on Bi-based 3D topological insulators. All of these materials families are predicted to be of the topological, twisty kind, and the final score from our experimental results from ARPES, combined with a varying mix of transport measurements in high magnetic fields, scanning tunneling microscopy and theoretical calculations of the electronic states is as follows. For SrMnSb2 the answer is no (= regular loop), for the hexaborides the jury is still out and for the Bi-based topological insulators the answer is definitely yes (= Möbius strip), whereby interesting effects involving extreme ultraviolet illumination offer new methods to understand and tune the twisty electronic states at the surface of these systems."--Samenvatting auteur.
Author: Shyama Varier Ramankutty Publisher: ISBN: 9789462339323 Category : Languages : en Pages : 151
Book Description
"Quantum materials pack the spooky properties of quantum mechanics into real-life materials you can make, pick up with tweezers and study in the lab. Those of interest to us show special electronic properties of great fundamental interest and have applications potential for future computer and electronics technologies. This thesis studies quantum materials in which the electronic states possess a special kind of twist, giving them a different topology to their regular electronic material cousins. Picturing the difference between a Möbius strip and a regular loop helps us get the idea of objects with differing topology. The research presented investigates the electronic states directly, using the photoelectric effect in angle resolved photoemission spectroscopy (ARPES) experiments, and was carried out on the candidate quasi-2D Dirac semimetal - SrMnSb2, a trio of rare earth hexaboride compounds, namely SmB6, YbB6 and CeB6, and on Bi-based 3D topological insulators. All of these materials families are predicted to be of the topological, twisty kind, and the final score from our experimental results from ARPES, combined with a varying mix of transport measurements in high magnetic fields, scanning tunneling microscopy and theoretical calculations of the electronic states is as follows. For SrMnSb2 the answer is no (= regular loop), for the hexaborides the jury is still out and for the Bi-based topological insulators the answer is definitely yes (= Möbius strip), whereby interesting effects involving extreme ultraviolet illumination offer new methods to understand and tune the twisty electronic states at the surface of these systems."--Samenvatting auteur.
Author: Jhih-Sheng Wu Publisher: ISBN: Category : Languages : en Pages : 116
Book Description
Two-dimensional materials are one-atom-thick crystals, which are stable under ambient conditions. Heterostructures by stacking of two-dimensional (2D) crystals via the van der Waals force provide a versatile platform for investigation of emergent properties of composite materials. In this thesis, I studied three 2D materials, graphene, Bi$_2$Se$_3$ and hexagonal boron nitride (hBN), of which the first two materials host 2D Dirac fermions. The core of this thesis is to study the transport and optical properties of 2D Dirac fermions interacted with their three-dimensional (3D) environments. In Chapter 2, we consider electron transport of graphene, adsorbing clusters of charged impurities. We model the clusters as circular barriers. We calculate the differential, total, and transport cross-sections for scattering of two-dimensional massless Dirac electrons by a circular barrier. For scatterer of a small radius, the cross-sections are dominated by quantum effects such as resonant scattering that can be computed using the partial-wave series. Scattering by larger size barriers is better described within the classical picture of reflection and refraction of rays, which leads to phenomena of caustics, rainbow, and critical scattering. Refraction can be negative if the potential of the scatterer is repulsive, so that a $p$-$n$ junction forms at its boundary. Qualitative differences of this case from the $n$-$N$ doping case are examined. Quantum interference effects beyond the classical ray picture are also considered, such as normal and anomalous diffraction, and also whispering-gallery resonances. Implications of these results for transport and scanned-probe experiments in graphene and topological insulators are discussed. In Chapter 3, we consider how the Dirac plasmons of Bi$_2$Se$_3$ are coupled with its phonon polaritons. Layered topological insulators, for example, Bi$_2$Se$_3$ are optically hyperbolic materials in a range of THz frequencies. Such materials possess deeply subdiffractional, highly directional collective modes: hyperbolic phonon-polaritons. In thin crystals the dispersion of such modes is split into discrete subbands and is strongly influenced by electron surface states. If the surface states are doped, then hybrid collective modes result from coupling of the phonon-polaritons with surface plasmons. The strength of the hybridization can be controlled by an external gate that varies the chemical potential of the surface states. Momentum-dependence of the plasmon-phonon coupling leads to a polaritonic analog of the Goos-Hänchen effect. Directionality of the polaritonic rays and their tunable Goos-Hänchen shift are observable via THz nanoimaging.
Author: Bertrand Duplantier Publisher: Birkhäuser ISBN: 3319325361 Category : Science Languages : en Pages : 139
Book Description
This fifteenth volume of the Poincare Seminar Series, Dirac Matter, describes the surprising resurgence, as a low-energy effective theory of conducting electrons in many condensed matter systems, including graphene and topological insulators, of the famous equation originally invented by P.A.M. Dirac for relativistic quantum mechanics. In five highly pedagogical articles, as befits their origin in lectures to a broad scientific audience, this book explains why Dirac matters. Highlights include the detailed "Graphene and Relativistic Quantum Physics", written by the experimental pioneer, Philip Kim, and devoted to graphene, a form of carbon crystallized in a two-dimensional hexagonal lattice, from its discovery in 2004-2005 by the future Nobel prize winners Kostya Novoselov and Andre Geim to the so-called relativistic quantum Hall effect; the review entitled "Dirac Fermions in Condensed Matter and Beyond", written by two prominent theoreticians, Mark Goerbig and Gilles Montambaux, who consider many other materials than graphene, collectively known as "Dirac matter", and offer a thorough description of the merging transition of Dirac cones that occurs in the energy spectrum, in various experiments involving stretching of the microscopic hexagonal lattice; the third contribution, entitled "Quantum Transport in Graphene: Impurity Scattering as a Probe of the Dirac Spectrum", given by Hélène Bouchiat, a leading experimentalist in mesoscopic physics, with Sophie Guéron and Chuan Li, shows how measuring electrical transport, in particular magneto-transport in real graphene devices - contaminated by impurities and hence exhibiting a diffusive regime - allows one to deeply probe the Dirac nature of electrons. The last two contributions focus on topological insulators; in the authoritative "Experimental Signatures of Topological Insulators", Laurent Lévy reviews recent experimental progress in the physics of mercury-telluride samples under strain, which demonstrates that the surface of a three-dimensional topological insulator hosts a two-dimensional massless Dirac metal; the illuminating final contribution by David Carpentier, entitled "Topology of Bands in Solids: From Insulators to Dirac Matter", provides a geometric description of Bloch wave functions in terms of Berry phases and parallel transport, and of their topological classification in terms of invariants such as Chern numbers, and ends with a perspective on three-dimensional semi-metals as described by the Weyl equation. This book will be of broad general interest to physicists, mathematicians, and historians of science.
Author: Eduard V Gorbar Publisher: World Scientific ISBN: 9811207364 Category : Science Languages : en Pages : 535
Book Description
The monograph reviews various aspects of electronic properties of Dirac and Weyl semimetals. After a brief discussion of 2D Dirac semimetals, a comprehensive review of 3D materials is given. The description starts from an overview of the topological properties and symmetries of Dirac and Weyl semimetals. In addition, several low-energy models of Dirac and Weyl quasiparticles are presented. The key ab initio approaches and material realizations are given. The monograph includes detailed discussions of the surface Fermi arcs, anomalous transport properties, and collective modes of Dirac and Weyl semimetals. Superconductivity in these materials is briefly addressed.
Author: San-Dong Guo Publisher: Frontiers Media SA ISBN: 2832531636 Category : Science Languages : en Pages : 114
Book Description
The fascinating two-dimensional (2D) materials are being unconsciously applied in various fields from science to engineering, which is benefited from the glamorous physical and chemical properties of mechanics, optics, electronics, and magnetism. The representative 2D thermoelectric/piezoelectric materials can directly convert thermal/mechanical energy into electrical energy, which can resolve the energy issues and avoid further environmental deterioration. The thermoelectric or piezoelectric properties of various 2D materials, such as graphene, hexagonal boron nitride, black phosphorus, transition metal dichalcogenides (TMDs), arsenene, metal carbides and nitrides (MXenes), and so on, have been investigated in detail. Although tremendous progress has been achieved in the past few years, these properties still need to be improved for their practical application by designing new 2D materials, strain engineering, chemical functionalization, etc. In addition to this, in 2D materials, there are many other novel physical properties, such as magnetism, topology, valley, and so on. The combination of thermoelectricity/piezoelectricity with other unique properties may lead to novel device applications or scientific breakthroughs in new physics. Overall, the emergence of 2D thermoelectric and piezoelectric materials has expanded energy conversion research dramatically. By combing this new device concept with the novel 2D materials, original devices should have potential applications in energy harvesting.
Author: Artem V. Pronin Publisher: Springer Nature ISBN: 3031356373 Category : Technology & Engineering Languages : en Pages : 141
Book Description
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.
Author: Alain Diebold Publisher: Springer Nature ISBN: 3030803236 Category : Technology & Engineering Languages : en Pages : 495
Book Description
This book covers the optical and electrical properties of nanoscale materials with an emphasis on how new and unique material properties result from the special nature of their electronic band structure. Beginning with a review of the optical and solid state physics needed for understanding optical and electrical properties, the book then introduces the electronic band structure of solids and discusses the effect of spin orbit coupling on the valence band, which is critical for understanding the optical properties of most nanoscale materials. Excitonic effects and excitons are also presented along with their effect on optical absorption. 2D materials, such as graphene and transition metal dichalcogenides, are host to unique electrical properties resulting from the electronic band structure. This book devotes significant attention to the optical and electrical properties of 2D and topological materials with an emphasis on optical measurements, electrical characterization of carrier transport, and a discussion of the electronic band structures using a tight binding approach. This book succinctly compiles useful fundamental and practical information from one of the fastest growing research topics in materials science and is thus an essential compendium for both students and researchers in this rapidly moving field.
Author: Hiroki Isobe Publisher: Springer ISBN: 9811037434 Category : Technology & Engineering Languages : en Pages : 143
Book Description
This thesis elucidates electron correlation effects in topological matter whose electronic states hold nontrivial topological properties robust against small perturbations. In addition to a comprehensive introduction to topological matter, this thesis provides a new perspective on correlated topological matter. The book comprises three subjects, in which electron correlations in different forms are considered. The first focuses on Coulomb interactions for massless Dirac fermions. Using a perturbative approach, the author reveals emergent Lorentz invariance in a low-energy limit and discusses how to probe the Lorentz invariance experimentally. The second subject aims to show a principle for synthesizing topological insulators with common, light elements. The interplay between the spin–orbit interaction and electron correlation is considered, and Hund's rule and electron filling are consequently found to play a key role for a strong spin–orbit interaction important for topological insulators. The last subject is classification of topological crystalline insulators in the presence of electron correlation. Unlike non-interacting topological insulators, such two- and three-dimensional correlated insulators with mirror symmetry are demonstrated to be characterized, respectively, by the Z4 and Z8 group by using the bosonization technique and a geometrical consideration.
Author: Frank Ortmann Publisher: John Wiley & Sons ISBN: 3527681582 Category : Technology & Engineering Languages : en Pages : 432
Book Description
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.
Author: Shyama Varier Ramankutty
Author: Shyama Varier Ramankutty
Author: Boris Pavlovic
Author: Jhih-Sheng Wu
Author: Bertrand Duplantier
Author: Eduard V Gorbar
Author: San-Dong Guo
Author: Artem V. Pronin
Author: Alain Diebold
Author: Hiroki Isobe
Author: Frank Ortmann