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Nematicity In Electron Doped Iron Pnictide Superconductors
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Book Synopsis Nematicity in Electron-Doped Iron-Pnictide Superconductors by : Hong Yi Chen
Download or read book Nematicity in Electron-Doped Iron-Pnictide Superconductors written by Hong Yi Chen and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The nature of the nematicity in iron pnictides is studied with a proposed magnetic fluctuation. The spin-driven order in the iron-based superconductor has been realized in two categories: stripe SDW state and nematic state. The stripe SDW order opens a gap in the band structure and causes a deformed Fermi surface. The nematic order does not make any gap in the band structure and still deforms the Fermi surface. The electronic mechanism of nematicity is discussed in an effective model by solving the self-consistent Bogoliubov-de Gennes equations. The nematic order can be visualized as crisscross horizontal and vertical stripes. Both stripes have the same period with different magnitudes. The appearance of the orthorhombic magnetic fluctuations generates two uneven pairs of peaks at ±π0 and 0±π in its Fourier transformation. In addition, the nematic order breaks the degeneracy of dxz and dyz orbitals and causes the elliptic Fermi surface near the Γ point. The spatial image of the local density of states reveals a dx2-y2-symmetry form factor density wave.
Book Synopsis Nematicity in iron-based superconductors by : Qisi Wang
Download or read book Nematicity in iron-based superconductors written by Qisi Wang and published by Frontiers Media SA. This book was released on 2023-02-15 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Electronic Nematicity in Iron-based Superconductors by : Hsueh-Hui Kuo
Download or read book Electronic Nematicity in Iron-based Superconductors written by Hsueh-Hui Kuo and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Emerging evidence for the presence of strongly anisotropic electronic states in the underdoped regime of both cuprate and iron-based high temperature superconductors suggests the possibility of an important role for electronic nematic order in these materials. The central theme of my thesis work has been the experimental study of electronic nematicity in iron-based superconductors via measurement of resistivity anisotropy. To do this, I have developed several new experimental techniques, on the one hand enabling detwinning of sub-mm size single crystals in the broken-symmetry orthorhombic state, and on the other hand revealing the nematic susceptibility in the high-symmetry tetragonal state. A major part of my thesis work has involved measurement of the elastoresistance; that is, the change in the resistance of a material as a consequence of the strains that it experiences. In this thesis, I will show how differential elastoresistance measurements can directly reveal the nematic susceptibility of a material in the tetragonal state. I will introduce the appropriate tensor formalism necessary to describe these measurements, and describe an experimental technique to determine these coefficients using piezoelectric stacks to provide anisotropic bi-axial strain. Results in the tetragonal state of various underdoped families based on the parent compound BaFe2As2 explicitly demonstrate that the tetragonal-to-orthorhombic structural transition in these materials is fundamentally driven by an electronic nematic instability. These results also suggest that the resistivity anisotropy in the paramagnetic orthorhombic state is dominated by the Fermi surface anisotropy, rather than an anisotropy in the scattering rate. Finally, similar measurements of a wide variety of optimally doped iron-pnictides and iron-chalcogenides reveal that a divergence of the nematic susceptibility in the B2g symmetry channel appears to be a generic feature of optimally-doped iron-based superconductors. In addition to the above, I also employ a mechanical detwinning technique to reveal the resistivity anisotropy in the orthorhombic state of the same Fe-based superconductors. For the isovalently-substituted material BaFe2(As1-xPx)2, these measurements reveal a strong coupling between external stress and both the Neel temperature and the superconducting critical temperature.
Book Synopsis On the Properties of Novel Superconductors by : Heshmatollah Yavari
Download or read book On the Properties of Novel Superconductors written by Heshmatollah Yavari and published by BoD – Books on Demand. This book was released on 2020-07-29 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the discovery of superconductivity, a great number of theoretical and experimental efforts have been made to describe this new phase of matter that emerged in many body systems. In this regard, theoretical models have been presented; the most famous of which was the BCS theory that can only describe conventional superconductors. With the discovery of new class superconductors, the superconducting mechanism became a new challenge in the field of condensed matter physics. This unexpected discovery opened a new area in the history of superconductivity, and experimental researchers started trying to find new compounds in this class of superconductors. These superconductors are often characterized by the anisotropic character in the superconducting gap function with nodes along a certain direction in the momentum space. Since the pairing interaction has an important role in the superconducting gap structure, its determination is very important to explain the basic pairing mechanism.In this regard, this book includes valuable theoretical and experimental discussions about the properties of superconductors. Here you will find valuable research describing the properties of unconventional superconductors.
Book Synopsis The Iron Pnictide Superconductors by : Ferdinando Mancini
Download or read book The Iron Pnictide Superconductors written by Ferdinando Mancini and published by Springer. This book was released on 2017-05-25 with total page 197 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Elastoresistance of Iron-based Superconductors by : Johanna Palmstrom
Download or read book Elastoresistance of Iron-based Superconductors written by Johanna Palmstrom and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Strong electronic nematic fluctuations have been discovered near optimal doping for several families of Fe-based superconductors, raising the question of what role, if any, these fluctuations might play in the superconducting pairing interaction. Underdoped Fe-based superconductors undergo a second order tetragonal-to-orthorhombic structural transition driven by electronic nematic order that accompanies or precedes an antiferromagnetic transition and borders the superconducting dome. In the tetragonal phase Fe-based superconductors are highly sensitive to perturbations of the same symmetry as the nematic order, such as antisymmetric (in this case B2g) strain. Elastoresistivity is described by a high rank tensor (fourth-rank +) as it relates changes in resistivity (second-rank) to strain (second-rank) experienced by a material and is a sensitive probe of broken symmetries. Previously, elastoresistivity measurements of the linear resistivity response to antisymmetric strain have revealed a divergent electronic nematic susceptibility in underdoped materials and has been used to characterize the nematic fluctuations in the tetragonal phase above the zero-field superconducting dome. In this work, I develop two new extensions to elastoresistivity measurements in order to probe the effects of electronic nematic fluctuations in greater detail in a representative family of these materials, the prototypical electron-doped pnictide Ba(Fe(1-x)Cox)2As2. First, I go beyond the first order response via a measurement of the nonlinear elastoresistivity. I find that the strong nematic fluctuations play a large role in the isotropic electronic response of these materials--as evidenced by a diverging nonlinear symmetric elastoresistivity response to antisymmetric strain. Second, I performed elastoresistivity measurements in magnetic fields large enough to suppress superconductivity to investigate the potential that the nematic fluctuations are related to a quantum critical point. I do not observe a magnetic field dependence of the nematic fluctuations and find that they continue to grow with decreasing temperature beneath the zero-field superconducting dome. I performed high magnetic field measurements on samples with a fine distribution of dopings and find that close to the putative quantum critical point, the nematic susceptibility appears to obey power law behavior over almost a decade of variation in composition. This is consistent with basic notions of nematic quantum criticality which, for clean systems, is associated with power law scaling in both doping and temperature. Paradoxically, however, I also find that the temperature dependence of the nematic susceptibility for compositions close to the critical value cannot be described by a single power law.
Book Synopsis Non-Universal Superconducting Gap Structure in Iron-Pnictides Revealed by Magnetic Penetration Depth Measurements by : Kenichiro Hashimoto
Download or read book Non-Universal Superconducting Gap Structure in Iron-Pnictides Revealed by Magnetic Penetration Depth Measurements written by Kenichiro Hashimoto and published by Springer Science & Business Media. This book was released on 2013-02-12 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Neutron Scattering Study of the Iron Based Superconductors by : Miaoyin Wang (Researcher in physics)
Download or read book Neutron Scattering Study of the Iron Based Superconductors written by Miaoyin Wang (Researcher in physics) and published by . This book was released on 2013 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: In most iron-based and copper-oxide superconductors, the Tc̳ [superconducting critical temperature] gradually increases upon charge carrier doping or isovalent doping. In the under-doped regime of electron-doped BaFe2As2 [Barium Iron 2 Arsenic 2], the superconductivity appears before the complete suppression of AF [antiferromagnetic] long-range order, creating a SC-AF [superconducting-antiferromagnetic] coexisting area. The interplay between long-range magnetic order and superconductivity was studied using a triple-axis thermal neutron spectrometer under an in-plane magnetic field. The suppression of superconductivity and the enhancement of long-range AF order were discovered under 11 Tesla, suggesting the competing nature of these two phases and the itinerant nature of iron-pnictides. We also measured the evolution of the neutron spin resonance in under-doped BaFe1̣ 925Ni0̣ 075As2 [Barium Iron 1.925 Nickel 0.075 As 2] and in over-doped BaFe1̣ 85Ni0̣ 15As2 [Barium Iron 1.85 Nickel 0.15 As 2]. Combining the previous results, we were able to compare the evolution of the neutron spin resonance energies in both BaFe2−x̳Nix̳As2 [Barium Iron (2-x) Nickel (x) Arsenic 2] and BaFe2−x̳Cox̳As2 [Barium Iron (2-x) Cobalt (x) Arsenic 2]. In late 2010, another type of iron-based superconductor alkali iron selenide A0̣ 8Fe1̣ 6+y̳Se2 [Alkali 0.8 Iron (1.6+y) Selenium 2 ] (or "245 system") was discovered. It is a unique system among the family of unconventional (high-Tc̳ [superconducting critical temperature]) superconductors because of its novel phase diagram, insulating parent compounds and huge magnetic moment. Using the inelastic time-of-flight technique, we are able to show that the parent compound can be described well by a local Heisenberg model. The follow up experiments on a superconducting sample (below and above Tc̳) and insulating samples (below and above Tn̳ [Neel Temperature]) provide a more detailed comparison and show more evidence that the alkali iron selenide system is rather different from either itinerant iron-pnictides or local copper-oxide systems.
Book Synopsis Iron-Based Superconducting Thin Films by : Silvia Haindl
Download or read book Iron-Based Superconducting Thin Films written by Silvia Haindl and published by Springer Nature. This book was released on 2021-06-27 with total page 403 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a modern introduction to the growth, characterization, and physics of iron-based superconducting thin films. Iron pnictide and iron chalcogenide compounds have become intensively studied key materials in condensed matter physics due to their potential for high temperature superconductivity. With maximum critical temperatures of around 60 K, the new superconductors rank first after the celebrated cuprates, and the latest announcements on ultrathin films promise even more. Thin film synthesis of these superconductors began in 2008 immediately after their discovery, and this growing research area has seen remarkable progress up to the present day, especially with regard to the iron chalcogenides FeSe and FeSe1-xTex, the iron pnictide BaFe2-xCoxAs2 and iron-oxyarsenides. This essential volume provides comprehensive, state-of-the-art coverage of iron-based superconducting thin films in topical chapters with detailed information on thin film synthesis and growth, analytical film characterization, interfaces, and various aspects on physics and materials properties. Current efforts towards technological applications and functional films are outlined and discussed. The development and latest results for monolayer FeSe films are also presented. This book serves as a key reference for students, lecturers, industry engineers, and academic researchers who would like to gain an overview of this complex and growing research area.
Book Synopsis Electrodynamics of Solids by : Martin Dressel
Download or read book Electrodynamics of Solids written by Martin Dressel and published by Cambridge University Press. This book was released on 2002-01-17 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors of this book present a thorough discussion of the optical properties of solids, with a focus on electron states and their response to electrodynamic fields. A review of the fundamental aspects of the propagation of electromagnetic fields, and their interaction with condensed matter, is given. This is followed by a discussion of the optical properties of metals, semiconductors, and collective states of solids such as superconductors. Theoretical concepts, measurement techniques and experimental results are covered in three interrelated sections. Well-established, mature fields are discussed (for example, classical metals and semiconductors) together with modern topics at the focus of current interest. The substantial reference list included will also prove to be a valuable resource for those interested in the electronic properties of solids. The book is intended for use by advanced undergraduate and graduate students, and researchers active in the fields of condensed matter physics, materials science and optical engineering.
Book Synopsis Superconductivity and Superfluidity by : T. Tsuneto
Download or read book Superconductivity and Superfluidity written by T. Tsuneto and published by Cambridge University Press. This book was released on 1998-12-10 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt: This 1998 book describes the physics of superconductivity and superfluidity, macroscopic quantum phenomena found in many conductors at low temperatures and in liquid helium 4 and helium 3. In the first part of the book the author presents the mean field theory of generalized pair condensation. This is followed by a description of the properties of ordinary superconductors using BCS theory. The book then proceeds with expositions of strong coupling theory and the Ginzberg-Landau theory. The remarkable properties of superfluid helium 3 are then described, as an example of a superfluid with internal degrees of freedom. The topics covered are dealt with in a coherent manner, with all necessary theoretical background given. Recent topics in the field, such as the copper-oxide high temperature superconductors and exotic superconductivity of heavy fermion systems are discussed in the final chapter. This book will be of interest to graduate students and researchers in condensed matter physics, especially those working in superconductivity and superfluidity.
Book Synopsis Neutron Scattering Studies of Cuprates and Iron Pnictides by : Mengshu Liu (Physicist)
Download or read book Neutron Scattering Studies of Cuprates and Iron Pnictides written by Mengshu Liu (Physicist) and published by . This book was released on 2014 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presented within are neutron scattering studies of several different high temperature superconducting materials: BaFe1.9Ni0.1As2 [Barium Iron Nickel Arsenic], BaFe1.85Ni0.15As2 [Barium Iron Nickel Arsenic], Ba0.67K0.33Fe2As2 [Barium Potassium Iron Arsenic], and Pr0.88LaCe0.12CuO4-y [Praseodymium Lanthanum Cerium Copper Oxide]. The main focus is on the magnetic excitations within the systems. For BaFe1.9Ni0.1As2 [Barium Iron Nickel Arsenic], we measured the intensity of its magnetic excitations and compared the results with excitations in antiferromagnetic non-superconducting BaFe2As2 [Barium Iron Arsenic]. We find electron-doping only affects spin excitations below 100 meV while the total size of the magnetic moment and the energy distribution do not change much. It shows that the magnetic moments in both materials are similar to insulating copper oxides, an indicator of the importance of strong electron correlations in high temperature superconductivity. For both BaFe1.85Ni0.15As2 [Barium Iron Nickel Arsenic] and Ba0.67K0.33Fe2As2 [Barium Potassium Iron Arsenic], we use polarized inelastic neutron scattering to study their low-energy spin excitations and their spatial anisotropy. Our neutron polarization analysis reveals that magnetic excitations are isotropic for the in-plane and out-of-plane components in both the normal and superconducting states for BaFe1.85Ni0.15As2 [Barium Iron Nickel Arsenic], while in Ba0.67K0.33Fe2As2 [Barium Potassium Iron Arsenic] large difference in spin gaps were found. A comparison of these results with those of undoped BaFe2As2 [Barium Iron Arsenic] and optimally electron-doped BaFe1.9Ni0.1As2 [Barium Iron Nickel Arsenic] suggests that the spin anisotropy observed Ba0.67K0.33Fe2As2 [Barium Potassium Iron Arsenic] are likely due to their proximity to their parent compound, where spin anisotropy exists below TN [Neel Temperature], while the neutron spin resonance is isotropic in the overdoped regime, consistent with a singlet to triplet excitation. For as-grown and optimal superconducting Pr0.88LaCe0.12CuO4-y [Praseodymium Lanthanum Cerium Copper Oxide] (PLCCO), we measured their magnetic excitations over a wide energy range, and compared their corresponding results. The spectra is considerably larger throughout the whole zone in as-grown PLCCO, than in the optimal superconducting PLCCO, which is very different from the BaFe2As2 [Barium Iron Arsenic] system.
Book Synopsis Iron-Based Superconductivity by : Peter D. Johnson
Download or read book Iron-Based Superconductivity written by Peter D. Johnson and published by Springer. This book was released on 2015-01-06 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Phase Transitions and Renormalization Group by : Jean Zinn-Justin
Download or read book Phase Transitions and Renormalization Group written by Jean Zinn-Justin and published by Oxford University Press on Demand. This book was released on 2007-07-05 with total page 465 pages. Available in PDF, EPUB and Kindle. Book excerpt: No further information has been provided for this title.
Book Synopsis Superconductivity in Ternary Compounds II by : Merrill B. Maple
Download or read book Superconductivity in Ternary Compounds II written by Merrill B. Maple and published by Springer. This book was released on 2013-11-11 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Neutron Scattering Study of High Tc Superconductors by : Jun Zhao
Download or read book Neutron Scattering Study of High Tc Superconductors written by Jun Zhao and published by . This book was released on 2010 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: We carried out systematic neutron scattering experiments to investigate the magnetic properties and their relationship to the high-Tc superconductivity, when the materials are tuned from their antiferromagnetic (AF) parent compounds to the superconducting regime. We observed resonance mode in the electron doped cuprate Nd[subscript 1.85]Ce[subscript 0.15]CuO[subscript 4], demonstrating that the resonance is a general phenomenon in cuprate superconductors regardless of hole- or electron-doping. In Pr[subscript 0.88]LaCe[subscript 0.12]CuO[subscript 4], the local susceptibility displays two distinct energy scales that are broadly consistent with the bosonic modes revealed by scanning tunneling microscopy experiments. These results indicate the presence of very strong electron spin excitations couplings in electron doped cuprates. Shortly after the discovery of high-Tc superconductivity in the Fe pnictides, we discovered that the magnetic phase diagram of CeFeAsO[subscript 1-x]F[subscript x] is remarkably similar to that of the cuprates. Besides CeFeAsO, similar magnetic and lattice structures are also observed in PrFeAsO and SrFe[subscript 2]As[subscript 2] systems. Neutron scattering measurements show that in SrFe[subscript 2]As[subscript 2], the spectrum of magnetic excitations consists of a Bragg peak at the elastic position, a spin gap, and sharp spin-wave excitations at higher energies. Based on the observed dispersion relation, we estimated the effective magnetic exchange coupling using a Heisenberg model. In order to study the nature of the exchange interactions in the parent compound of Fe pnictides, we studied the high energy spin-wave excitations in CaFe2As2. Although the spin waves in the entire Brillouin zone can be described by an effective three-dimensional anisotropic Heisenberg Hamiltonian, the magnetism in this system is neither purely local nor purely itinerant; rather it is a complicated mix of the two. When the Fe pnictide is tuned into superconducting regime with doping, the low energy spin fluctuation is dominated by a resonance mode. In the optimally electron doped BaFe[subscript 1.9]Ni[subscript 0.1]As[subscript 2], application of a magnetic field that suppresses the superconductivity and superconducting gap energy also reduces the intensity and energy of the resonance. These results suggest that the energy of the resonance is proportional to the electron pairing energy, and thus indicate that spin fluctuations are intimately related to the mechanism of high Tc superconductivity.
Book Synopsis Phase Diagram and Magnetic Excitations of BaFe2-xNixAs2: A Neutron Scattering Study by : Xingye Lu
Download or read book Phase Diagram and Magnetic Excitations of BaFe2-xNixAs2: A Neutron Scattering Study written by Xingye Lu and published by Springer. This book was released on 2017-07-10 with total page 127 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
