Electron Phonon Interaction And Its Effects In Heavy Fermion Systems

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.

The book on Heavy-Fermion Systems is a part of the Book series "Handbook of Metal Physics", each volume of which is written to facilitate the research of Ph.D. students, faculty and other researchers in a specific area. The Heavy-Fermions (sometimes known as Heavy-Electrons) is a loosely defined collection of intermetallic compounds containing rare-earth (mostly Ce) or actinide (mostly U) elements. These unusual names were given due to the large effective mass (100-1,000 times greater than the mass of a free electron) below a critical temperature. They have a variety of ground states including superconducting, antiferromagnetic, paramagnetic or semiconducting. Some display unusual magnetic properties such as magnetic quantum critical point and metamagnetism. This book is essentially a summary as well as a critical review of the theoretical and experimental work done on Heavy Fermions. · Extensive research references. · Comprehensive review of a very rapidly growing number of theories. · Summary of all important experiments. · Comparison with other highly correlated systems such as High-Tc Superconductors. · Possible Technological applications.

Anomalous Rare Earths and Actinides: Valence Fluctuation and Heavy Fermions focuses on the characteristics, reactions, transformations, technologies, and processes involved in the study of anomalous rare earths and actinides. The selection first offers information on lanthanides and actinides and electronic structures in cerium monopnictides. Topics include rare earth metals with fluctuating valencies, 'normal' rare earth metals, and band calculation and Fermi surface. The text then elaborates on neutron scattering studies of anomalous rare earth compounds, including magnetic neutron scattering measurements, stability and localization of magnetic moments, and condensed state. The manuscript examines the transport properties of cerium monochalcogenides and pressure-volume relationships of cerium monochalcogenides and monopnictides. The text also ponders on the theory of anisotropic magnetic behavior in hybridizing actinide systems; band hybridization effects on indirect magnetic coupling of localized moments; and neutron scattering from transuranium materials. The selection is a dependable reference for readers interested in the research on anomalous rare earths and actinides.

Papers presented at the International Conference on Phonons in Condensed Materials, held at Bhopal during 20-23 January 2003.

Various experimental techniques for point contact production are described. Examples of point-contact spectra are presented for pure metals, alloys and compounds, as well as for semimetals and semiconductors, heavy fermion systems, Kond-lattices, mixed valence compounds and more. Superconducting point contacts are considered in respect to Andreev reflection and Josephson effects. Special attention is paid to contact conductance fluctuation, and new trends of research are outlined.

A large variety of materials prove to be fascinating in solid state and condensed matter physics. New materials create new physics, which is spearheaded by the international experimental expert, Prof Yoshichika Onuki. Among them, the f electrons of rare earth and actinide compounds typically exhibit a variety of characteristic properties, including spin and charge orderings, spin and valence fluctuations, heavy fermions, and anisotropic superconductivity. These are mainly manifestations of better competitive phenomena between the RKKY interaction and the Kondo effect. The present text is written so as to understand these phenomena and the research they prompt. For example, superconductivity was once regarded as one of the more well-understood many-body problems. However, it is, in fact, still an exciting phenomenon in new materials. Additionally, magnetism and superconductivity interplay strongly in heavy fermion superconductors. The understanding of anisotropic superconductivity and magnetism is a challenging problem in solid state and condensed matter physics. This book will tackle all these topics and more. Contents: Conduction Electrons and Fermi Surfaces Local Magnetic Moment Single Crystal Growth and Measuring Methods Itinerant 3d-electrons Heavy Fermions Superconductivity Readership: Graduate students and researchers interested and/or involved in single crystal growth, heavy fermions, superconductivity and related experimental methods. Keywords: Heavy Fermions;Strongly Correlated Electrons Systems;Magnetism;SuperconductivityReview: Key Features: Readers can understand the present frontiers of solid state and condensed matter physics, on the basis of fundamental ideas and formulae described in various related methods of measurement This paves the way for readers to participate in research concerning single crystal growth and characteristic properties in rare earth and actinide compounds

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.