Download or read book Heavy Fermion Superconductivity and Quantum Criticality in Ce and Pu Based 115 Materials written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Superconductivity Magnetism Quantum Criticality And Hidden Order In Quantum Materials written by Dom Lal Kunwar and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The heavy fermions (HF) are strongly correlated electron systems consisting of intermetallic compounds of lanthanides and actinides ions with f -electrons unfilled shells. These systems are very rich in physics and the interplay between competing interactions results in various interesting physical phenomena such as heavy fermion behavior, unconventional superconductivity, non-Fermi-liquid behavior, coexistence of superconductivity and magnetism, and quantum criticality. The origin of such phenomena comes from the interaction of itinerant conduction states with the partially filled 4f - or 5f -electron states of rare earth elements. The study of such important physical phenomena can be possible by tuning the system using nonthermal control parameters, such as chemical composition, magnetic field, and applied pressure. So, studying the chemical pressure effect on heavy fermion systems with or without magnetic field is an intriguing idea to construct various phase diagrams and study their phase transitions. We performed heat capacity (HC), magnetoresistance (MR), and resistivity measurements on the Ce-based 115 and U-based 122 heavy fermion materials at low temperatures. We studied the nature of the quantum critical point, second-order phase transition, and the possible interplay between superconductivity and magnetism. First, we were motivated by the possibility of observing the coexistence of magnetism and unconventional superconductivity in the heavy fermion Ce1-xSmxCoIn5 alloys. We performed specific heat, MR, and resistivity measurements in different magnetic fields. We investigated how the samarium substitution on the cerium site affects the magnetic-field-tuned quantum criticality of stoichiometric CeCoIn5. We have observed Fermi-liquid to non-Fermi-liquid crossovers in the temperature dependence of the electronic specific heat and resistivity at higher external magnetic fields. We obtained the magnetic-field-induced quantum critical point (HQCP) by extrapolating the crossover temperature to zero temperature. Furthermore, we performed a scaling analysis of the electronic specific heat and confirmed the existence of the QCP. According to our findings, the magnitude of (HQCP) decreases as the samarium content rises and ultimately becomes zero. The electronic specific heat and resistivity data reveal a zero-field QCP for xcr = 0.15, which falls inside the antiferromagnetic and superconducting coexistence region. Next, we performed measurements of the heat capacity as a function of temperature in a single crystals URu2-xOsxSi2. Our experimental results show that the critical temperature of the second-order phase transition increases while the value of the Sommerfeld coefficient in the ordered state decreases with an increase in osmium concentration. We also observed the increase in the magnitude of the heat capacity at the critical temperature and a broadening of the critical fluctuations region with an increase in Os concentration. We analyze the experimental data using the Haule- Kotliar model, which identifies the 'hidden order' transition in the parent material URu2Si2 as a transition to a state with nonzero hexadecapolar moment. We showed that our experimental results are consistent with this model. In conclusion, we studied the interplay between superconductivity and magnetism in Ce based 115 and U based 122 single crystal alloys using heat capacity, magnetoresistivity, and resistivity measurements in both cryogenic systems including He-4 and He-3. The understating of various phenomena in these heavy fermions could be helpful in developing higher transition temperature superconductors, energy storage devices, quantum computers, and memory devices in the future.

Download or read book Quantum Criticality and Unconventional Properties of Heavy Fermion Superconductor Ce1 xYbxCoIn5 written by Yogesh Pratap Singh and published by . This book was released on 2015 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current research interest in heavy fermion (HF) materials is for their unconventional superconductivity, their quantum critical behavior and the breakdown of Fermi liquid (FL) theory. Presently, we lack a universal understanding of the breakdown of the FL behavior in these materials. However, there are evidences which suggest that the breakdown of the FL behavior and the unconventional superconducting (SC) pairing could be the result of a zero temperature phase transition, taking place at a quantum critical point (QCP). Heavy fermions are f-electron materials in which local moments at each lattice site interact with the spin of the conduction electrons sitting at that site via an exchange coupling. There are two energy scales that result from this interaction, the Kondo temperature TK (temperature below which the local moments are screened by the spins of the conduction electrons), and the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, which characterize the induced coupling between two local moments. These two energy scales can be tuned by external parameters such as magnetic field, pressure, and chemical substitution. Such a tuning provides an opportunity to study the rich physics of these materials. This dissertation work presents experimental and theoretical studies on ab unique member of Ce-115 family of heavy fermions, i.e., Ce1-xYbxCoIn5. In the Ce-115 family of HFs, Cerium (Ce) contributes the f-electrons to form a Kondo lattice. The substitution of Ce ions by other rare earths is a widely used approach to study this system. Our selection of ytterbium for substituting Ce-site is unique in the sense that Yb appears in the intermediate valence state in this system (unlike any other substitution), thus giving rise to many of the unusual properties, which helped in the understanding the underlying physics of SC pairing, quantum criticality and non-Fermi liquid behavior in this HF. For the purpose of the studies presented in this dissertation, we utilized electronic, magneto- and thermal transport measurements. These measurements were done under high magnetic fields and pressures wherever needed. We developed a new method to identify the field-induced QCP in this material by studying its normal state. We utilized this method to locate QCP in the parent compound CeCoIn5 and determined its evolution with Yb doping in Ce1-xYbxCoIn5. Our findings show that quantum criticality in this system is suppressed by doping with Yb and a zero field QCP is obtained for the x = 0.20 Yb-doping level. Our studies also show the evolution of the many-body electronic state as the Kondo lattice of Ce moments is transformed into an array of Ce impurities with Yb-doping. Specifically, we observe a crossover from the predominantly localized Ce moment regime to the predominantly itinerant Yb f-electronic state regime. In the crossover regime, the magneto-transport behavior of the system indicates single impurity behavior of Ce ions. This result is surprising because the resistivity and specific heat measurements suggest significant amount of coherent scattering in the system. We attribute this unusual behavior to the hybridization of conduction electrons with mixed valence Yb ions, giving rise to an intermediate energy scale (TK ~ 14 K) between the single impurity regime of Ce and Ce Kondo lattice regime. Even more intriguing are the results at even higher Yb-doping levels. Large enough Yb concentrations show an increased coherence, unlike any other member of the Ce-115 family. We also identified another QCP at a higher Yb concentration of x = 0.75. An equally interesting feature in the doping dependence of this compound is the survival of NFL behavior throughout the phase diagram. The sub-linear temperature dependence of resistivity across the whole range of Yb concentrations suggests the presence of an unconventional scattering mechanism for the conduction electrons. Thus although the quantum spin fluctuations are suppressed at around 20 % of Yb doping, the NFL behavior is observed for the whole family. Our finding of an additional high doping QCP very well explains the large value of the Sommerfeld's coefficient and the persistent NFL behavior over the whole Yb-doping range. Given the complete suppression of the antiferromagnetic fluctuations for x > 0.20 and the very robust coherence and superconductivity, the possible electron pairing mechanism may involve an exchange of virtual magnetic fluctuations or a more unconventional mechanism involving virtual fluctuations into higher lying Ce crystalline field multiplets. We analyze theoretically the dependence of the superconducting critical temperature and Kondo lattice coherence temperature on pressure for both cases of clean and disordered systems. We use the approach of the large-N mean field theory, which works very well for Kondo lattice systems.

Download or read book Quantum Critical Phenomena of Valence Transition written by Shinji Watanabe and published by Springer Nature. This book was released on 2024-01-27 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book comprehensively presents an unconventional quantum criticality caused by valence fluctuations, which offers theoretical understanding of unconventional Fermi-liquid properties in cerium- and ytterbium-based heavy fermion metals including CeCu2(Si,Ge)2 and CeRhIn5 under pressure, and quasicrystal β-YbAlB4 and Yb15Al34Au51. The book begins with an introduction to fundamental concepts for heavy fermion systems, valence fluctuation, and quantum phase transition, including self-consistent renormalization group theory. A subsequent chapter is devoted to a comprehensive description of the theory of the unconventional quantum criticality based on a valence transition, featuring explicit temperature dependence of various physical quantities, which allows for comparisons to relevant experiments. Lastly, it discusses how ubiquitous the valence fluctuation is, presenting candidate materials not only in heavy fermions, but also in strongly correlated electrons represented by high-Tc superconductor cuprates. Introductory chapters provide useful materials for learning fundamentals of heavy fermion systems and their theory. Further, experimental topics relevant to valence fluctuations are valuable resources for those who are new to the field to easily catch up with experimental background and facts.

Download or read book Quantum Criticality and Fermisurface Instabilities Investigation by Pressure and Quantum Oscillation Measurements on Ce and Ybbased Heavy Fermion Compounds written by Mounir Boukahil and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The superconductivity had been thought to be incompatible with the magnetism, because the former originates from the weak attractive leading to the formation of Cooper pairs, whereas the latter is based on the strong Coulomb repulsive force, leading also to strong electronic correlations. Unconventional superconductors,which include heavy fermion systems, high-Tc cuprates, organic superconductors, and iron-pnictides, is a major topic of condensed matter physics. In all these systems, it has been understood that magnetism can even plays an important role for the pairing mechanism, so that both phenomena can coexist and even favour each other.Our target is on heavy fermion systems, namely uranium and rare earth compounds, where the 5f or 4f electrons which have a dual nature (itinerant/localized), play an important role. More precisely, we will focus on the ferromagnetic superconductors and their quantum criticality. In this field, new materials open new frontiers of research. The student will participate in this stream. He will learn and develop the fundamental crystal growth techniques, such as Czochralski, flux, and Bridgeman method. Since high quality single crystals are essential to elucidate the superconducting properties, a lot of efforts will be devoted to improve the quality of the samples. The next target is the quantum oscillation measurements, which allow a detailed microscopic observation of the heavy electronic state and of the topology of the Fermi surface. They require both very low temperature and high fields, like the study of the field induced superconducting phases in these compounds (like URhGe or UCoGe). The student will perform the measurements under extreme conditions, namely high fields up to 15T in SPSMS, or up to 30T in LNCMI, at low temperatures down to 30 mK, and high pressure up to 3 GPa.From the educational point of view, it is ideal that the student starts to synthesize a material, characterizes it, performs the low temperature measurements by him/herself throughout the PhD period, and get used to the exciting measurements under extreme conditions in a large scale facility like the LNCMI. Such a wide spectrum is rather rare in Europe, but our group ("SPSMS/LNCMI) can provide such a unique opportunity, helping the student to become an independent researcher. It should be noted that the experiments in SPSMS and LNCMI are quite complementary each other. For quantum oscillation study, high fields, low temperatures and high quality singles are inevitably important. In general, the precise measurements at high fields up to 15T would be enough in order to determine the Fermi surface topology and the effective mass, which canbe done in SPSMS. However, the specific case, such as Lifshitz transition, field induced quantum critical phenomena, requires higher fields than 15T, which can be achieved by the resistive magnet in LNCMI.This project is supported by the ANR (CORMAT, SINUS) and the ERC starting grant “NewHeavyFermion”.Recently in SPSMS we purchased a top-loading dilution refrigerator for the quantum oscillation measurements, and started the installation. By the end of this summer, hopefully we detect the first de Haas-van Alphen signal at high fields up to 15T and at temperatures down to 30mK. Furthermore, we started to install the flux crystal growth equipment this month, involving the reconstruction of the room for the safe treatment of uranium compounds.

Download or read book The Heaviest Metals written by William J. Evans and published by John Wiley & Sons. This book was released on 2019-01-08 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt: An authoritative survey of the science and advanced technological uses of the actinide and transactinide metals The Heaviest Metals offers an essential resource that covers the fundamentals of the chemical and physical properties of the heaviest metals as well as the most recent advances in their science and technology. The authors – noted experts in the field – offer an authoritative review of the actinide and transactinide elements, i.e., the elements from actinium to lawrencium as well as rutherfordium through organesson, the current end of the periodic table, element 118. The text explores the history of the metals, their occurrence and issues of production, and covers a broad range of chemical subjects including environmental concerns and remediation approaches. The authors also offer information on the most recent and emerging applications of the metals, such as in superconducting materials, catalysis, and research into medical diagnostics. This important resource: Provides an overview of the science and advanced technological uses of the actinide and transactinide metals Describes the basic chemical and physical properties of the heaviest metals, and discusses the challenges and opportunities for their technological applications Contains accessible information on the fundamental features of the heaviest metals, special requirements for their experimental study, and the critical role of computational characterization of their compounds Highlights the most current and emerging applications in areas such as superconducting materials, catalysis, nuclear forensics, and medicine Presents vital contemporary issues of the heaviest metals Written for graduate students and researchers working with the actinide and transactinide elements, industrial and academic inorganic and nuclear chemists, and engineers, The Heaviest Metals is a comprehensive volume that explores the fundamental chemistry and properties of the heaviest metals, and the challenges and opportunities associated with their present and emerging technological uses.

Download or read book Electrodynamics of Quantum Critical Conductors and Superconductors written by Uwe Santiago Pracht and published by Springer. This book was released on 2017-12-14 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents and discusses recent optical low-temperature experiments on disordered NbN, granular Al thin-films, and the heavy-fermion compound CeCoIn5, offering a unified picture of quantum-critical superconductivity. It provides a concise introduction to the respective theoretical models employed to interpret the experimental results, and guides readers through in-depth calculations supplemented with supportive figures in order to both retrace the interpretations and span the bridge between experiment and state-of-the art theory.

Download or read book Journal of the Physical Society of Japan written by and published by . This book was released on 2007 with total page 1376 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heavy Fermions Quantum Criticality and Unconventional Superconductivity in Filled Skutterudites and Related Materials written by and published by . This book was released on 2015 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main goal of this program was to explore the possibility of novel states and behaviors in Pr-based system exhibiting quantum critical behavior, PrOs4Sb12. Upon small changes of external parameter, such as magnetic field, physical properties of PrOs4Sb12 are drastically altered from those corresponding to a superconductor, to heavy fermion, to field-induced ordered phase with primary quadrupolar order parameter. All these states are highly unconventional and not understood in terms of current theories thus offer an opportunity to expand our knowledge and understanding of condensed matter. At the same time, these novel states and behaviors are subjects to intense international controversies. In particular, two superconducting phases with different transition temperatures were observed in some samples and not observed in others leading to speculations that sample defects might be partially responsible for these exotic behaviors. This work clearly established that crystal disorder is important consideration, but contrary to current consensus this disorder suppresses exotic behavior. Superconducting properties imply unconventional inhomogeneous state that emerges from unconventional homogeneous normal state. Comprehensive structural investigations demonstrated that upper superconducting transition is intrinsic, bulk, and unconventional. The high quality of in-house synthesized single crystals was indirectly confirmed by de Haas-van Alphen quantum oscillation measurements. These measurements, for the first time ever reported, spanned several different phases, offering unprecedented possibility of studying quantum oscillations across phase boundaries.

Download or read book Exploring Heavy Fermion Materials Near a Quantum Critical Point written by Sooyoung Jang and published by . This book was released on 2015 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results for two categories of heavy fermion systems : (1) a new type of non-centrosymmetric heavy fermion system R2TM12Pn7 (R = rare earth, TM = transition metal, Pn = P, As), and (2) Yb substitution in CeCoIn5, which is a heavy fermion superconductor, Ce1-xYbxCoIn5, are described. The phenomena seen in the system R2TM12Pn7 are discussed in terms of strong hybridization between the localized f-electron states and the conduction electron states, such as a crossover between Fermi liquid and non-Fermi liquid behavior in Yb2Ni12P7, or the presence of a large value of the Sommerfeld coefficient, [gamma] ~ 650 mJ/mol Sm K2 in Sm2Ni12P7. The extraordinary electronic phenomena found in the system Ce1-xYbxCoIn5 include Yb valence fluctuations, a change in the Fermi surface topology, and suppression of the quantum critical field occurring at a nominal concentration of x ~ 0.2. However, the suppression of the superconducting critical temperature with nominal Yb concentration x for bulk single crystals is much weaker than that observed in thin film samples. The actual Yb composition of bulk single crystals is found to be about 1/3 of the nominal concentration, resolving the discrepancy between the variation of the physical properties of Ce1-xYbxCoIn5 single crystals and thin films with Yb concentrations.

Download or read book Yb based Heavy Fermion Compounds and Field Tuned Quantum Criticality written by Eundeok Mun and published by . This book was released on 2010 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Quantum Critical Behavior and Superconductivity in New Multi site Cerium Heavy Fermion Compound Ce3PtIn11 written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Quantum Criticality in the Heavy Fermion Superconductor Cerium cobalt indium microform written by Johnpierre Paglione and published by Library and Archives Canada = Bibliothèque et Archives Canada. This book was released on 2005 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heavy Fermions written by Aline Ramires Neves de Oliveira and published by . This book was released on 2015 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: Condensed matter physics is an area of research which lies at a sweet spot between two complementary perspectives: the atomistic point of view which takes into account all the details of the system of interest; and the framework of universality and emergent phenomena, which allows us to make drastic simplifications to the microscopic description of materials while still being able to explain much of the experimentally observed phenomena. This thesis addresses problems from both perspectives, focusing on heavy fermion systems. Heavy fermion systems are prototype materials for the study of strongly correlations and quantum criticality. Theoretical understanding of these systems is important for the design of new materials and for the fundamental understanding of quantum critical phenomena. This thesis is strongly motivated by recent experiments in an intrinsically quantum critical material, beta-YbAlB4. This system shows anomalous critical exponents in transport and thermodynamics. In Chapter 2 we construct a phenomenological theory for the heavy fermion metal beta-YbAlB4 based on the Anderson model, taking into account the peculiarities of this specific material. We analyze the consequences of a non-trivial, momentum-dependent, hybridization matrix between f-electrons and conduction electrons, which gives rise to a nodal metal with unusual dispersion and singular thermodynamic properties, in accordance with experiments. In Chapter 3 we analyze the Electron Spin Resonance experiments in this same material and propose a theory including spin-orbit coupling, crystal electric fields and hyperfine coupling which can account for many of the features of the experimentally observed signal. Within a broader perspective on heavy fermion systems, the absence of a single unified theoretical description which can account for the plethora of phenomena observed in this class of materials also motivates us to consider new theoretical approaches. In Chapter 4 we generalize the construction of supersymmetric spin representations in the large-N limit, now with symplectic symmetry, and explore its properties. We apply the supersymmetric symplectic-N spin representation to two toy models in Chapter 5, and find promising results for a future unified picture of heavy fermion systems.

Download or read book Introduction to Unconventional Superconductivity written by V.P. Mineev and published by CRC Press. This book was released on 1999-09-21 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: Unconventional superconductivity (or superconductivity with a nontrivial Cooper pairing) is believed to exist in many heavy-fermion materials as well as in high temperature superconductors, and is a subject of great theoretical and experimental interest. The remarkable progress achieved in this field has not been reflected in published monographs and textbooks, and there is a gap between current research and the standard education of solid state physicists in the theory of superconductivity. This book is intended to meet this information need and includes the authors' original results.

Download or read book Introduction to Many Body Physics written by Piers Coleman and published by Cambridge University Press. This book was released on 2015-11-26 with total page 815 pages. Available in PDF, EPUB and Kindle. Book excerpt: A modern, graduate-level introduction to many-body physics in condensed matter, this textbook explains the tools and concepts needed for a research-level understanding of the correlated behavior of quantum fluids. Starting with an operator-based introduction to the quantum field theory of many-body physics, this textbook presents the Feynman diagram approach, Green's functions and finite-temperature many-body physics before developing the path integral approach to interacting systems. Special chapters are devoted to the concepts of Fermi liquid theory, broken symmetry, conduction in disordered systems, superconductivity and the physics of local-moment metals. A strong emphasis on concepts and numerous exercises make this an invaluable course book for graduate students in condensed matter physics. It will also interest students in nuclear, atomic and particle physics.

Download or read book Topological Insulators and Topological Superconductors written by B. Andrei Bernevig and published by Princeton University Press. This book was released on 2013-04-07 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: This graduate-level textbook is the first pedagogical synthesis of the field of topological insulators and superconductors, one of the most exciting areas of research in condensed matter physics. Presenting the latest developments, while providing all the calculations necessary for a self-contained and complete description of the discipline, it is ideal for graduate students and researchers preparing to work in this area, and it will be an essential reference both within and outside the classroom. The book begins with simple concepts such as Berry phases, Dirac fermions, Hall conductance and its link to topology, and the Hofstadter problem of lattice electrons in a magnetic field. It moves on to explain topological phases of matter such as Chern insulators, two- and three-dimensional topological insulators, and Majorana p-wave wires. Additionally, the book covers zero modes on vortices in topological superconductors, time-reversal topological superconductors, and topological responses/field theory and topological indices. The book also analyzes recent topics in condensed matter theory and concludes by surveying active subfields of research such as insulators with point-group symmetries and the stability of topological semimetals. Problems at the end of each chapter offer opportunities to test knowledge and engage with frontier research issues. Topological Insulators and Topological Superconductors will provide graduate students and researchers with the physical understanding and mathematical tools needed to embark on research in this rapidly evolving field.