Electronic Transitions And Correlation Effects
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Electronic Transitions And Correlation Effects
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Author : Johan Jönsson
language : en
Publisher: Linköping University Electronic Press
Release Date : 2020-03-17
Electronic Transitions And Correlation Effects written by Johan Jönsson and has been published by Linköping University Electronic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020-03-17 with categories.
Macroscopic properties of real materials, such as conductivity, magneticproperties, crystal structure parameters, etc. are closely related or evendetermined by the configuration of their electrons, characterized by electronicstructure. By changing the conditions, e.g, pressure, temperature, magnetic/electric field, chemical doping, etc. one can modify the electronic structure ofsolids and therefore induce a phase transition(s) between different electronic andmagnetic states. One famous example is a Mott metal-to-insulator phase transition,at which a material undergoes a significant, often many orders of magnitude, changeof conductivity caused by the interplay between itineracy and localization of thecarriers. Electronic topological transitions (ETT) involvechanges in the topology of a metal's Fermi surface. This thesis investigates theeffect of such electronic transitions in various materials, ranging from pureelements to complex compounds. To describe the interplay between electronic transitionsand properties of real materials,different state-of-the-art computational methods are used. The densityfunctional theory(DFT), as well as the DFT + U method, is used to calculatestructural properties. The validity of recently introduced exchange-correlationfunctionals, such as the strongly constrained and appropriately normed (SCAN)functional, is also assessed for magnetic elements. In order toinclude dynamical effects of electron interactions we use the DFT + dynamical meanfield theory (DFT + DMFT) method. Experiments in hcp-Os have reported peculiarities in the ratio betweenlattice parameters at high pressure. Previous calculations have suggested these transitions maybe related to ETTs and even crossings of core levels at ultra high pressure. Inthis thesis it is shownthat the crossing of core levels is a general feature of heavy transitionmetals. Experiments have therefore been performed to look for indications ofthis transition in Ir using X-ray absorption spectroscopy. In NiO, strongrepulsion between electrons leads to a Mott insulating state at ambientconditions. It has long been predicted that high pressure will lead to aninsulator-to-metal transition. This has been suggested to be accompanied by aloss of magnetic order, and a structural phase transition. In collaboration withexperimentalists we look for thistransition by investigating the X-ray absorption spectra as well as themagnetic hyperfine field. We find no evidence of a Mott transition up to 280GPa. In the Mott insulator TiPO4, application of external pressure has beensuggested to lead to a spin-Peierls transition at room temperature. Weinvestigate the dimerisation and the magnetic structure of TiPO4 at high pressure.As pressure is increased further, TiPO4 goes through a metal to insulatortransition before an eventual crystallographic phase transition. Remarkably, thenew high pressure phases are found to be insulators; the Mott insulating stateis restored. MAX phases are layered materials that combinemetallic and ceramic properties and feature layers of M-metal and X-C or N atomsinterconnected by A-group atoms. Magnetic MAX-phases with their low dimensionalmagnetism are promising candidates for applications in e.g., spintronics.The validity of various theoretical approaches are discussed in connection tothe magnetic MAX-phase Mn2GaC. Using DFT and DFT + DMFT we consider the hightemperature paramagnetic state, and whether the magnetic moments are formed bylocalized or itinerant electrons. Ett materials makroskopiska egenskaper, såsom ledningsförmåga, magnetiska egenskaper, kristallstrukturparametrar, etc. är relaterade till, eller till och med bestämda av elektronernas konfiguration, vilken karakteriseras av elektronstrukturen. Genom att ändra förhållandena, till exempel via tryck, temperatur, magnetiska och/eller elektriska fält, dopning, etc. är det möjligt att modifiera elektronstrukturen hos ett material, och därigenom inducera fasövergångar mellan olika magnetiska och elektron-tillstånd. Mott metall-till-isolator övergången är ett berömt exempel på en fasövergång, då ett material genomgår en omfattande, ofta flera tiopotenser, förändring i ledningsförmåga, orsakad av samspelet mellan ambulerande och lokaliserade laddningsbärare. Vid en elektronisk-topologisk övergång (eng. electronic topological transition, ETT) sker förändringar i elektronernas energifördelning vilket modifierar materialets Fermi-yta. I den här avhandlingen undersöks dylika övergångar i olika material, från rena grundämnen till komplicerade föreningar. Flera olika toppmoderna beräkningsmetoder används för att redogöra för samspelet mellan elektroniska fasövergångar och egenskaper hos riktiga material. Täthetsfunktionalterori (eng. density functional theory, DFT), samt DFT + U, har används för att beräkna strukturella egenskaper. Lämplighetsgraden i att använda nyligen publicerade exchangecorrelation- funktionaler, såsom SCAN (eng. strongly constrained and appropriately normed), för att beskriva magnetiska grundämnen undersöks även. För att inkludera dynamiska elektronkorrelationer använder vi metoden DFT + dynamisk medelfältteori (eng. dynamical mean field theory, DMFT). Experiment utförda på hcp-Os vid högt tryck visar underliga hopp i kvoten mellan gitterparametrar. Tidigare beräkningar har indikerat att dessa övergångar kan vara relaterade till elektronisk-topologiska övergångar och korsande av kärntillstånd. I den här avhandlingen visas också att korsning av kärntillstånden är en generell egenskap hos tunga övergångsmetaller. Därför utförs röntgenabsorptionsexperiment på Ir för att leta efter tecken på denna typ av övergång. Övergångsmetalloxiden NiO har sedan länge förutspåtts genomgå en isolator till metall Mott-övergång. Det har föreslagits att denna övergång sker vid höga tryck i samband med att materialets magnetiska ordning försvinner och en strukturell övergång sker. I samarbete med experimentalister letar vi efter denna övergång genom att studera röntgenabsorptionsspektra och det magnetiska hyperfina fältet. Vi ser inga indikationer på en Mott-övegång, upp till ett tryck på 280 GPa. Det har föreslagits att Mott-isolatorn TiPO4 genomgår en så kallad spin-Peierls-övergång, vid rumstemperatur, när tryck appliceras. Vi undersöker dimeriseringen och den magnetiska strukturen i TiPO4 som funktion av tryck. Vid höga tryck genomgår TiPO4 ytterligare övergångar, från en isolerande till en metallisk fas för att slutligen genomgå en strukturell övergång. De nya högtrycksfaserna visar sig anmärkningsvärt vara Mott-isolatorer. MAX-faser är en grupp material med specifik kristallstruktur, som kombinerar egenskaper från keramiska material och metaller. En MAX-fas består av lager av M –metall-atomer – och X – kol- eller kväveatomer – vilka sammanbinds av atomer från grupp A. Magnetiska MAX-faser som visar magnetiska egenskaper, liknande de för lågdimensionella material, är lovande kandidater för applikation inom exempelvis spinntronik. Den här avhandlingen undersöker lämplighetsgraden i att använda diverse teoretiska metoder för att beskriva magnetiska MAX-faser. Med hjälp av DFT och DFT + DMFT undersöker vi den paramagnetiska högtemperaturfasen och huruvida de magnetiska momenten bildas av lokaliserade eller ambulerande elektroner.
Electron Electron Correlation Effects In Low Dimensional Conductors And Superconductors
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Author : Alexandr A. Ovchinnikov
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06
Electron Electron Correlation Effects In Low Dimensional Conductors And Superconductors written by Alexandr A. Ovchinnikov and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Science categories.
Advances in the physics and chemistry of low-dimensional systems have been really magnificent in the last few decades. Hundreds of quasi-one-dimensional and quasi-two-dimensional systems have been synthesized and studied. The most popular representatives of quasi-one-dimensional materials are polyacethylenes CH [1] and conducting donor-acceptor molecular crystals TIF z TCNQ. Examples of quasi-two-dimensional systems are high temperature su perconductors (HTSC) based on copper oxides LA2CU04, YBa2Cu306+y and organic superconductors based on BEDT -TIP molecules. The properties of such one- and two-dimensional materials are not yet fully understood. On the one hand, the equations of motion of one-dimensional sys tems are rather simple, which facilitates rigorous solutions of model problems. On the other hand, manifestations of various interactions in one-dimensional systems are rather peculiar. This refers, in particular, to electron--electron and electron-phonon interactions. Even within the limit of a weak coupling con stant electron--electron correlations produce an energy gap in the spectrum of one-dimensional metals implying a Mott transition from metal to semiconductor state. In all these cases perturbation theory is inapplicable. Which is one of the main difficulties on the way towards a comprehensive theory of quasi-one-dimensional systems. - This meeting held at the Institute for Theoretical Physics in Kiev May 15-18 1990 was devoted to related problems. The papers selected for this volume are grouped into three sections.
Electronic Structure Correlation Effects And Physical Properties Of D And F Metals And Their Compounds
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Author : Valentin Yu Irkhin
language : en
Publisher: Cambridge Int Science Publishing
Release Date : 2007
Electronic Structure Correlation Effects And Physical Properties Of D And F Metals And Their Compounds written by Valentin Yu Irkhin and has been published by Cambridge Int Science Publishing this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with Science categories.
The book includes all main physical properties of d- and f-transition-metal systems and corresponding theoretical concepts. Special attention is paid to the theory of magnetism and transport phenomena. Some examples of non-traditional questions which are treated in detail in the book: the influence of density of states singularities on electron properties; many-electron description of strong itinerant magnetism; mechanisms of magnetic anisotropy; microscopic theory of anomalous transport phenomena in ferromagnets. Besides considering classical problems of solid state physics as applied to transition metals, modern developments in the theory of correlation effects in d- and f-compounds are considered within many-electron models. The book contains, where possible, a simple physical discussion. More difficult questions are considered in Appendices.
Electron Correlation Dynamics In Atomic Collisions
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Author : J. H. McGuire
language : en
Publisher: Cambridge University Press
Release Date : 1997-03-20
Electron Correlation Dynamics In Atomic Collisions written by J. H. McGuire and has been published by Cambridge University Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 1997-03-20 with Science categories.
Describes the dynamics of electron correlation in multi-electron transitions in atomic, molecular and optical physics.
Correlation Effects In Low Dimensional Electron Systems
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Author : Ayao Okiji
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06
Correlation Effects In Low Dimensional Electron Systems written by Ayao Okiji and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Science categories.
Correlation Effects in Low-Dimensional Electron Systems describes recent developments in theoretical condensed-matter physics, emphasizing exact solutions in one dimension including conformal-field theoretical approaches, the application of quantum groups, and numerical diagonalization techniques. Various key properties are presented for two-dimensional, highly correlated electron systems.
Concepts In Electron Correlation
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Author : Alex C. Hewson
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06
Concepts In Electron Correlation written by Alex C. Hewson and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Science categories.
The NATO sponsored Advanced Research Workshop on "Concepts in Electron Correlation" took place on the Croatian island of Hvar during the period from the 29th of September to the 3rd of October, 2002. The topic of electron correlation is a fundamental one in the field of condensed matter, and one that is being very actively studied both experimentally and theoretically at the present time. The manifestations of electron cor relation are diverse, and play an important role in systems ranging from high temperature superconductors, heavy fermions, manganite compounds with colossal magnetoresistance, transition metal compounds with metal insulator transitions, to mesoscopic systems and quantum dots. The aim of the workshop was to provide an opportunity for a dialogue between exper imentalists and theoreticians to assess the current state of understanding, and to set an agenda for future work. There was also a follow-up workshop on the same topic where the presentations included more background and introductory material for younger researchers in the field. The papers presented in these proceedings clearly demonstrate the di versity of current research on electron correlation. They show that real progress is being made in characterising systems experimentally and in developing theoretical approaches for a quantitative comparison with ex periment. The more one learns, however, the more there is to understand, and many of the contributions help to map out the territory which has yet to be explored. We hope that the articles in this volume will be a stimulus for such future work.
Electronically Highly Correlated Ternary Transition Metal Oxides
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Author : Alexander Krimmel
language : en
Publisher: diplom.de
Release Date : 2005-04-15
Electronically Highly Correlated Ternary Transition Metal Oxides written by Alexander Krimmel and has been published by diplom.de this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005-04-15 with Science categories.
Introduction: Transition metal oxides represent a large class of compounds with a uniquely wide range of electronic properties. Some of these properties, like the magnetism of loadstone, have been known since antiquity. Others, like high-temperature superconductivity have been discovered only recently and indeed would have been thought of being impossible 20 years ago. Transition metal oxides may be good insulators, semiconductors, metals or superconductors. Many of them display a metal-to-insulator transition (MIT) as a function of an external control parameter (usually temperature, pressure or chemical composition). The differences of electrical conductivity are also reflected by drastic changes of other physical properties related to the electronic structure. The electrical, magnetic and optical properties of transition metal oxides find a rich field of important technical applications. A classical example is the wide use of ferrites in electronic devices. Further examples of suitable technological applications include wide gap semiconductors, superconductors and thermoelectric materials, to mention just a few. Apart from these exciting electronic properties, some transition metal oxides exhibit a remarkable mechanical and high-temperature stability together with a strong resistance against corrosion, thus forming ideal coating materials. Several transition metal oxides may also serve as catalysts. It was the discovery of high-temperature superconductivity in the cuprates and, subsequently, of the colossal magneto-resistance effect (CMR) in the manganates that triggered a tremendous research effort in transition metal oxides during the last decade. [...]
Relativistic And Electron Correlation Effects In Molecules And Solids
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Author : G.L. Malli
language : en
Publisher: Springer Science & Business Media
Release Date : 2013-11-21
Relativistic And Electron Correlation Effects In Molecules And Solids written by G.L. Malli and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-11-21 with Science categories.
The NATO Advanced Study Institute (ASI) on "R@lativistic and Electron Correlation Effects in Molecules and Solids", co-sponsored by Simon Fraser University (SFU) and the Natural Sciences and Engineering Research Council of Canada (NSERC) was held Aug 10- 21, 1992 at the University of British Columbia (UBC), Vancouver, Canada. A total of 90 lecturers and students with backgrounds in Chemistry, Physics, Mathematics and various interdisciplinary subjects attended the ASI. In my proposal submitted to NATO for financial support for this ASI, I pointed out that a NATO ASI on the effects of relativity in many-electron systems was held ten years ago, [See G.L. Malli, (ed) Relativistic Effects in Atoms, Molecules and Solids, Plenum Press, Vol B87, New York, 1983]. Moreover, at a NATO Advanced Research Workshop (ARW) on advanced methods for molecular electronic structure "an assessment of state-of the-art of Electron Correlation ... " was carried out [see C.E. Dykstra, (ed), Advanced Theories and Computational Approaches to the Electronic Structure of Molecules, D. Reidel Publishin~ Company, Vol C133, Dordrecht, The Netherlands 1984]. However, during the last five years, it has become clear that the relativistic and electron correlation effects must be included in the theoretical treatment of many-electron molecules and solids of heavy elements (with Z > 70). Molecules and clusters containing heavy elements are of crucial importance in a number of areas of Chemistry and Physics such as nuclear fuels, catalysis, surface science, etc.
Desorption Induced By Electronic Transitions Diet V
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Author : Alan R. Burns
language : en
Publisher: Springer Science & Business Media
Release Date : 2013-03-07
Desorption Induced By Electronic Transitions Diet V written by Alan R. Burns and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-03-07 with Science categories.
This volume in the Springer Series on Surface Sciences presents a recent account of advances in the ever-broadening field of electron-and photon-stimulated sur face processes. As in previous volumes, these advances are presented as the proceedings of the International Workshop on Desorption Induced by Electronic Transitions; the fifth workshop (DIET V) was held in Taos, New Mexico, April 1-4, 1992. It will be abundantly clear to the reader that "DIET" is not restricted to desorption, but has for several years included photochemistry, non-thermal surface modification, exciton self-trapping, and many other phenomena that are induced by electron or photon bombardment. However, most stimulated surface processes do share a common physics: initial electronic excitation, localization of the excitation, and conversion of electronic energy into nuclear kinetic energy. It is the rich variation of this theme which makes the field so interesting and fruitful. We have divided the book into eleven parts in order to emphasize the wide range of materials that are examined and to highlight recent experimental and theoretical advances. Naturally, there is considerable overlap between sections, and many papers would be appropriate in more than one part. Part I focuses on perhaps the most active area in the field today: electron attachment. Here the detection and characterization of negative ions formed by attachment of elec trons supplied externally from the vacuum are discussed. In addition, the first observations of negative ions formed by substrate photoelectrons are presented.
Electron Correlation In Molecules And Condensed Phases
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Author : Norman H. March
language : en
Publisher: Springer Science & Business Media
Release Date : 1996-10-31
Electron Correlation In Molecules And Condensed Phases written by Norman H. March and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 1996-10-31 with Science categories.
This reference describes the latest research on correlation effects in the multicenter problems of atoms, molecules, and solids. The author utilizes first- and second-order matrices, including the important observable electron density rho(r), and the Green function for discussing quantum computer simulations. With its focus on concepts and theories, this volume will benefit experimental physicists, materials scientists, and physical and inorganic chemists as well as graduate students.