Interplay of Magnetic, Orthorhombic, and Superconducting Phase Transitions in Iron Based Superconductors PDF Download

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 115

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Author: Peter D. Johnson
Publisher: Springer
ISBN: 3319112546
Category : Technology & Engineering
Languages : en
Pages : 452

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This volume presents an in-depth review of experimental and theoretical studies on the newly discovered Fe-based superconductors. Following the Introduction, which places iron-based superconductors in the context of other unconventional superconductors, the book is divided into three sections covering sample growth, experimental characterization, and theoretical understanding. To understand the complex structure-property relationships of these materials, results from a wide range of experimental techniques and theoretical approaches are described that probe the electronic and magnetic properties and offer insight into either itinerant or localized electronic states. The extensive reference lists provide a bridge to further reading. Iron-Based Superconductivity is essential reading for advanced undergraduate and graduate students as well as researchers active in the fields of condensed matter physics and materials science in general, particularly those with an interest in correlated metals, frustrated spin systems, superconductivity, and competing orders.

Author: Kenichiro Hashimoto
Publisher: Springer Science & Business Media
ISBN: 4431542949
Category : Technology & Engineering
Languages : en
Pages : 135

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In this book the author presents two important findings revealed by high-precision magnetic penetration depth measurements in iron-based superconductors which exhibit high-transition temperature superconductivity up to 55 K: one is the fact that the superconducting gap structure in iron-based superconductors depends on a detailed electronic structure of individual materials, and the other is the first strong evidence for the presence of a quantum critical point (QCP) beneath the superconducting dome of iron-based superconductors. The magnetic penetration depth is a powerful probe to elucidate the superconducting gap structure which is intimately related to the pairing mechanism of superconductivity. The author discusses the possible gap structure of individual iron-based superconductors by comparing the gap structure obtained from the penetration depth measurements with theoretical predictions, indicating that the non-universal superconducting gap structure in iron-pnictides can be interpreted in the framework of A1g symmetry. This result imposes a strong constraint on the pairing mechanism of iron-based superconductors. The author also shows clear evidence for the quantum criticality inside the superconducting dome from the absolute zero-temperature penetration depth measurements as a function of chemical composition. A sharp peak of the penetration depth at a certain composition demonstrates pronounced quantum fluctuations associated with the QCP, which separates two distinct superconducting phases. This gives the first convincing signature of a second-order quantum phase transition deep inside the superconducting dome, which may address a key question on the general phase diagram of unconventional superconductivity in the vicinity of a QCP.

Author: Qisi Wang
Publisher: Frontiers Media SA
ISBN: 2832514707
Category : Science
Languages : en
Pages : 120

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Author: Jong-Hoon Kang
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Superconductivity often emerges on the border of a broken-symmetry phase in iron-based high-temperature superconductors. Previous bulk studies have shown that the broken symmetry phase is suppressed by chemical doping or pressure in a parent material and the superconducting transition temperature is highest for regular tetrahedral geometry. However, little is known about how to deliberately maintain a regular tetrahedron through a tetragonal-to-orthorhombic phase transition. I present an epitaxial thin films approach for the atomic structure design of iron-based superconductors to understand the relation between structure and properties, and enhance the superconducting transition temperature (Tc). Epitaxial thin film heterostructures and superlattices lead to the study of interface engineering and strain engineering for manipulating atomic configurations at the interface. Furthermore, the suppression of an orthorhombic phase transition by dimension control is suggested, which enables atomic geometry to a reach regular tetrahedron with two independent structural parameters such as tetragonality and orthorhombicity. Finally, I will describe the influence of atomic geometry on Tc, which potentially reveals an intriguing interplay between magnetism and superconductivity.

Author: Xingye Lu
Publisher: Springer
ISBN: 981104998X
Category : Technology & Engineering
Languages : en
Pages : 127

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This book studies the structural, magnetic and electronic properties of, as well as magnetic excitations in, high-temperature BaFe2-xNixAs2 superconductors using neutron diffraction and neutron spectroscopic methods. It describes the precise determination of the phase diagram of BaFe2-xNixAs2, which demonstrates strong magnetoelastic coupling and avoided quantum criticality driven by short-range incommensurate antiferromagnetic order, showing cluster spin glass behavior. It also identifies strong nematic spin correlations in the tetragonal state of uniaxial strained BaFe2-xNixAs2. The nematic correlations have similar temperature and doping dependence as resistivity anisotropy in detwinned samples, which suggests that they are intimately connected. Lastly, it investigates doping evolution of magnetic excitations in overdoped BaFe2-xNixAs2 and discusses the links with superconductivity. This book includes detailed neutron scattering results on BaFe2-xNixAs2 and an introduction to neutron scattering techniques, making it a useful guide for readers pursuing related research.

Author: Aliaksei Charnukha
Publisher: Springer Science & Business Media
ISBN: 3319011928
Category : Technology & Engineering
Languages : en
Pages : 139

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This thesis combines highly accurate optical spectroscopy data on the recently discovered iron-based high-temperature superconductors with an incisive theoretical analysis. Three outstanding results are reported: (1) The superconductivity-induced modification of the far-infrared conductivity of an iron arsenide with minimal chemical disorder is quantitatively described by means of a strong-coupling theory for spin fluctuation mediated Cooper pairing. The formalism developed in this thesis also describes prior spectroscopic data on more disordered compounds. (2) The same materials exhibit a sharp superconductivity-induced anomaly for photon energies around 2.5 eV, two orders of magnitude larger than the superconducting energy gap. The author provides a qualitative interpretation of this unprecedented observation, which is based on the multiband nature of the superconducting state. (3) The thesis also develops a comprehensive description of a superconducting, yet optically transparent iron chalcogenide compound. The author shows that this highly unusual behavior can be explained as a result of the nanoscopic coexistence of insulating and superconducting phases, and he uses a combination of two complementary experimental methods - scanning near-field optical microscopy and low-energy muon spin rotation - to directly image the phase coexistence and quantitatively determine the phase composition. These data have important implications for the interpretation of data from other experimental probes.

Author: Ferdinando Mancini
Publisher: Springer
ISBN: 3319561170
Category : Technology & Engineering
Languages : en
Pages : 197

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This book covers different aspects of the physics of iron-based superconductors ranging from the theoretical, the numerical and computational to the experimental ones. It starts from the basic theory modeling many-body physics in Fe-superconductors and other multi-orbital materials and reaches up to the magnetic and Cooper pair fluctuations and nematic order. Finally, it offers a comprehensive overview of the most recent advancements in the experimental investigations of iron based superconductors.

Author: Walter O. Uhoya
Publisher:
ISBN:
Category : Ferromagnetic materials
Languages : en
Pages : 279

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Interplay of pressure and chemistry play an important role in discovery of novel properties such as high temperature superconductivity (high-Tc). In 2008, Hosono et al discovered superconductivity at 26 K in iron-based layered LaFeAsO (1-x)Fx. This observation was a surprise since iron based compounds are generally known to be magnetic and non-superconducting. This was quickly followed by the discovery of high temperature superconductivity in a second class of Fe-based layered pnictides AFe2As2 (1-2-2) (A= Ba, Sr, Ca, Eu). The undoped (parent) 1-2-2 compounds are non-superconducting at ambient pressure but become superconducting when their structures are tuned by the application of high pressure or through chemical doping. Application of high pressures is advantageous over chemical doping in that it provides a clean method to tune the electronic properties that determine the superconducting and magnetic states of the novel materials. Interplay of pressure induced structural transitions, magnetic and superconducting properties of Fe-based materials is not well understood and this may form a foundation for testing present theories, discovering materials with higher-Tc for wide industrial applications close to room temperature, and may lead to better theories for solving the long standing problem of high-Tc superconductivity. In my work, I have used designer diamond anvil cell (DAC) to study the electrical transport properties of 1-2-2 parents of iron based superconductors under extreme conditions of pressure and low temperatures. I have used high pressure and low temperature time of flight neutron diffraction technique at the Spallation Neutron Source and synchrotron x-ray diffraction techniques at the Advance Photon Source to determine and refine the crystallographic parameters of the 1-2-2 materials under extreme conditions, and to relate their transport and structural properties under high pressures. My works have resulted into a discovery of anomalous compressibility and a concurrent tetragonal to collapsed tetragonal (T-cT) isostructural phase transition in 1-2-2 parents of iron-based superconductors. We showed that the anomaly is a common phenomenon for pure and doped ThCr2Si2 type pnictides of the type AT2As2 (A= divalent alkaline earth or rare earth element Ba, Ca, Sr, Eu; T=transition metal). We determine a general relation for predicting isostructural T-cT phase transition pressure for any 1-2-2 pnictide given its ambient pressure volume. Our work suggests that the collapsed tetragonal phase is non-superconducting. We have establish how onset of pressure induced superconductivity (TConset) in 1-2-2 parent materials depends on the compression behavior of As-Fe-As tetrahedral bond angles, tetragonal lattice parameter c, Fe2As2 layer thickness and As-As inter-atomic bond distance for parent 1-2-2 materials. The evolution of pressure driven tetragonal distortion, quantitative crystallographic parameters and pressure-volume equation of state for 1-2-2 materials under high pressures are presented up to 70 GPa and low temperatures down to 4 K.

Author: Franziska Hammerath
Publisher: Springer Science & Business Media
ISBN: 3834824232
Category : Science
Languages : en
Pages : 183

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Nuclear Magnetic Resonance (NMR) has been a fundamental player in the studies of superconducting materials for many decades. This local probe technique allows for the study of the static electronic properties as well as of the low energy excitations of the electrons in the normal and the superconducting state. On that account it has also been widely applied to Fe-based superconductors from the very beginning of their discovery in February 2008. This dissertation comprises some of these very first NMR results, reflecting the unconventional nature of superconductivity and its strong link to magnetism in the investigated compounds LaO1–xFxFeAs and LiFeAs.