Those well-intending workers, especially theorists, who have viewed hungrily the mixed valence problem, but have not yet made the bold leap, might be comforted to learn that the Rochester conference left the virginal state of that problem essentially intact. That is not to say that the event was prosaic. Indeed, the conferees exhibited a level of effervescence appropriate to the freshness and challenge of the problem at hand. If the meeting failed to solve major questions, it at least established several guidelines. One is that future experimental efforts, at least on a short time scale, might be spent most profitably on those substances which exhibit consistent, and hence probably intrinsic, behavior from laboratory to laboratory. A recurring message, not always subtle, to the·theorists was that piecemeal approaches to the mixed valence problem, characteristic of much of the work to date, are of limited usefulness. For at the core of the problem one has a melange of boot-strapping interac tions which must be sorted out and dealt with properly. Para phrasing Phil Anderson (see Epilogue), the mixed valence problem is in the same category of problems which are failing to be done in field theory these days.
The understanding of electronic behaviour in solids when (some of) the valence electrons have both localized and band-like characteristics is one of the central problems of physics and chemistry in the second half of this century. Many advances have indeed been made using highly sophisticated techniques and concepts. Our objectives in bringing together specialists from different areas was cross-fertilization of ideas and redefinition of bottlenecks and problems. The testimony of the participants and the book which follows indicate a fair degree of success. This book is a record of discussions aimed at digestion and reassessment of some of the recent major advances in our understanding of narrow bands. Note that we expressly asked participants to give a short readable account of the major problems in their field and not to emphasize their latest results to be as "technical" as they might be in a normal scientific article. We did not ask for complete reviews of what was going on in the field and this book should not be read as such. Neither should it be approached as the sort of educational text which the NATO ASI proceedings are supposed to be. We have tried to produce a useable account of a workshop in which an attempt was made to define real problems and to distinguish them from illusory problems.
Theoretical physicist and Nobel Laureate Philip Anderson has been described as one of the most imaginative of condensed matter physicists working today. His achievements have not merely constituted significant discoveries in their own right, but have also frequently set the agenda for the work of others. His pioneering contributions include the Anderson model of magnetic impurities and the concept of localisation, both of which were mentioned in his Nobel Prize citation. He also worked on the study of spin glasses, the fluctuating valence problem and superexchange. He predicted the existence of superfluidity in He-3 and provided a microscopic explanation, and was involved in the discovery of the Josephson effect. The understanding of topics as diverse as the Higgs mechanism, pulsar glitches, high Tc superconductivity, flux creep and flow in superconducting magnets and the solution of the Kondo problem has benefited from his contributions.This volume contains a discriminating selection of the many topics on which Philip Anderson has worked. Some of the papers included are now hard to find elsewhere, and each has been embellished with commentary on how they came to be written. Anderson has also provided an entertaining introduction setting out his philosophy of what is important in science.
This volume and its two companion volumes, entitled Tetrahedrally-Bonded Amorphous Semiconductors and Physics of Disordered Materials, are our way of paying special tribute to Sir Nevill Mott and to express our heartfelt wishes to him on the occasion of his eightieth birthday. Sir Nevill has set the highest standards as a physicist, teacher, and scientific leader. Our feelings for him include not only the respect and admiration due a great scientist, but also a deep affection for a great human being, who possesses a rare combination of outstanding personal qualities. We thank him for enriching our lives, and we shall forever carry cherished memories of this noble man. Scientists best express their thanks by contributing their thoughts and observations to a Festschrift. This one honoring Sir Nevill fills three volumes, with literally hundreds of authors meeting a strict deadline. The fact that contributions poured in from all parts of the world attests to the international cohesion of our scientific community. It is a tribute to Sir Nevill's stand for peace and understanding, transcending national borders. The editors wish to express their gratitude to Ghazaleh Koefod for her diligence and expertise in deciphering and typing many of the papers, as well as helping in numerous other ways. The blame for the errors that remain belongs to the editors.
The aim of this book is to review recent achievements in thetheoretical investigations of the electronic structure, optical, magneto-optical (MO), and x-ray magnetic circular dichroism (XMCD)properties of compounds and Multilayered structures.Chapter 1 of this book is of an introductory character and presentsthe theoretical foundations of the band theory of solids such as thedensity functional theory for ground state properties of solidsincluding local density approximation (LDA). It also presents somemodifications to the LDA, such as gradient correction, self-interaction correction, LDA+U method, orbital polarizationcorrection, GW approximation, and dynamical mean- field theory. Thedescription of the magneto-optical effects and linear response theoryare also presented.The book describes the MO properties for a number of 3d materials, such as elemental ferromagnetic metals (Fe, Co and Ni) andparamagnetic metals in external magnetic fields (Pd and Pt), someimportant 3d compounds such as XPt3 (X=V, Cr, Mn, Fe and Co), Heusleralloys, chromium spinel chalcogenides, MnB and strongly correlatedmagnetite Fe304. It also describes the recent achievements in both theexperimental and theoretical investigations of the electronicstructure, optical and MO properties of transition metal multilayeredstructures (MLS).The book presents also the MO properties of f band ferromagneticmaterials: Tm, Nd, Sm, Ce and La monochalcogenides, some important Y
The story of heavy fermions (HF) begun with the discovery of the low temperature behaviour of CeAl3 by Andres et al. in the year 1975 took the momentum after the discovery of superconductivity in CeCu2Si2 by Steglich et al. in the year 1979 . Though HF behaviour is common in the rare-earth elements like Ce, Yb and actinides like U, it is also found to exist in some of the praseodymium (Pr), samarium (Sm) , plutonium (Pu) and more recently in neptunium (Np) systems. These compounds are characterized by the presence of partially filled f-electron bands. At high temperatures, these magnetic moments manifest themselves as a weakly interacting set of local moments of the f electrons with Curie-Weiss susceptibility that coexists with light s or d conduction electrons. But at low temperature, these f-electrons hybridize with conduction electrons near Fermi level via Kondo spin fluctuation which happens through constant exchange spin-flip transition of f-electrons and band electrons in the vicinity of Fermi level. This process leads to a strong mixing of Fermi electrons with the localized f-electrons which is manifested in a renormalization of the Fermi surface and a drastic enhancement of the effective mass of the electrons at Fermi level. Further, in HF systems, electron-phonon interaction (EPI) contributes a lot in manifestation of some of the anomalous behaviour relating to elastic constant, ultrasonic attenuation & sound velocity, anisotropic Fermi surface, Kondo volume collapse etc. In this PhD thesis book in title “Electron phonon interaction and its effect in heavy fermion (HF) systems” the author tries to put some light into the behavoiour of Electron-phonon interaction in describing some of the properties of HF systems at low temperatures. In this 1 st edition, the book has been presented in multicolour edition with profuse colour illustrations so as to increase its clarity, understand ability and legibility, especially of the figures depicted to explain the low temperature behaviour of HF systems. It is hoped that the present book will serve its purpose in attracting young researchers to the field of HF systems. It is my foremost duty to express my deep sense of gratitute to my supervisor Dr. Pratibindhya Nayak , Professor Emeritus, School of Physics, Sambalpur University, Odisha, for his able guidance at every stage of this work.. His innovative methods and inspirational guidance have largely contributed to the conceptualization of the form and content of this book. I am indebted to my family members for their constant support. I am sincerely thankful to the publisher, Newredmars Education to bring my works into light in form of a book Healthy criticism and suggestions for further improvement of the book are solicited.
