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Probing The Symmetry Breaking Phases In Iron Based Superconductors With Combined Strain Transport And X Ray Techniques
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Book Synopsis Probing the Symmetry-breaking Phases in Iron-based Superconductors with Combined Strain, Transport and X-ray Techniques by : Joshua Javier Sanchez
Download or read book Probing the Symmetry-breaking Phases in Iron-based Superconductors with Combined Strain, Transport and X-ray Techniques written by Joshua Javier Sanchez and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spontaneous rotational symmetry breaking phases, such as the electronic nematic phase and charge and spin stripe phases, are commonly found in the phase diagram of strongly correlated materials including many of the high-temperature superconductors. This thesis is essentially a study of how tuning parameters, namely applied uniaxial stress and applied magnetic field, can interact with the rotational symmetry-breaking order parameters of these phases, either to probe the system and better understand its intrinsic properties or to create new states in the system that are not spontaneously generated. This thesis discusses the development of a methodology which combines synchrotron x-ray techniques and transport measurements of a single crystal sample mounted to a uniaxial stress device. This methodology is used in iron-based high temperature superconducting materials to probe the nematic and magnetic phases. In Co-doped BaFe2As2, the coupling between electronic nematicity, the crystal lattice and the resistivity anisotropy is probed by strain, and a temperature and phase independent transport-structural correspondence is demonstrated. In EuFe2As2, the effects of nematicity on the Eu localized magnetic order is demonstrated from a strongly anisotropic antiferromagnetic coupling between Eu moments. While the work in this thesis is primarily focused on iron-based superconductors, these ideas are very general to the field of condensed matter physics, and this methodology of applied fields combined with x-ray measurements developed here is broadly applicable to systems with structural domains, large magnetoelastic coupling, and other strongly correlated electron effects.
Book Synopsis Probing Quantum Criticality in an Iron-based Superconductor with Symmetry-breaking Strain by : Thanapat Worasaran
Download or read book Probing Quantum Criticality in an Iron-based Superconductor with Symmetry-breaking Strain written by Thanapat Worasaran and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, I study the effect of the symmetry-preserving strain and the orthogonal antisymmetric strain to the critical temperature of the nematic phase transition (Ts) in a prototypical iron-based superconductor, BaFe2As2. The result establishes both strains as effective tuning parameters. This perspective is the utilized to systematically study the effect of these strain to Ts in the cobalt-doping series of BaFe2As2. A power-law behavior of the critical temperature was observed as a function of the combined tuning parameters, which is a linear combination the strains and the cobalt concentration. This provides the first clear evidence for power-law behavior of the critical temperature as a function of non-thermal tuning parameters. Lastly, I proposed an experiment that permits the measurement of the nematic susceptibility while continuously tuning the critical temperature with strain.
Book Synopsis Broken Rotational Symmetry in Iron Based Superconductors by : Jiun-Haw Chu
Download or read book Broken Rotational Symmetry in Iron Based Superconductors written by Jiun-Haw Chu and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: High-temperature superconductivity often emerges in the proximity of a symmetry-breaking ground state in strongly interacting electronic materials. In the case of the superconducting iron pnictides, in addition to the antiferromagnetic ground state of the parent compounds, a ubiquitous but small structural distortion breaks the crystal C4 rotational symmetry in the underdoped part of the phase diagram. It has been proposed that this structural transition is driven by an electronic nematic phase transition, below which the electronic system spontaneously organizes with an orientational order without developing additional spatial periodic order. In this thesis I show how the effects of this electronic nematic order can be explicitly revealed by observing the response of the system to in-plane uniaxial stress. I present transport measurements of single crystal samples of various iron-based superconductors held under an in-situ tunable strain at temperatures above the phase transition, which explicitly confirm that the structural transition is fundamentally driven by a thermodynamic instability in the electronic part of the free energy. I will also discuss the nematic fluctuations prevailing throughout the overdoped part of the phase diagram, which suggests that a quantum phase transition occurs at the optimal doped composition. Finally, I will describe the in-plane resistivity anisotropy measurements of detwinned samples at temperatures below phase transition, which potentially reveals an intriguing interplay between topological protected Dirac pockets and spin/orbital ordering.
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 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 Conventional Empirical Law Reverses in the Phase Transitions of 122-type Iron-based Superconductors by :
Download or read book Conventional Empirical Law Reverses in the Phase Transitions of 122-type Iron-based Superconductors written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Phase transition of solid-state materials is a fundamental research topic in condensed matter physics, materials science and geophysics. It has been well accepted and widely proven that isostructural compounds containing different cations undergo same pressure-induced phase transitions but at progressively lower pressures as the cation radii increases. However, we discovered that this conventional law reverses in the structural transitions in 122-type iron-based superconductors. In this report, a combined low temperature and high pressure X-ray diffraction (XRD) measurement has identified the phase transition curves among the tetragonal (T), orthorhombic (O) and the collapsed-tetragonal (cT) phases in the structural phase diagram of the iron-based superconductor AFe2As2 (A = Ca, Sr, Eu, and Ba). The cation radii dependence of the phase transition pressure (T → cT) shows an opposite trend in which the compounds with larger ambient radii cations have a higher transition pressure.
Book Synopsis Probing Nano-scale Atomic and Electronic Structures of Iron-based Superconductors by :
Download or read book Probing Nano-scale Atomic and Electronic Structures of Iron-based Superconductors written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Phase Transitions and Anomalous Compressibility in 1-2-2 Fe-based Superconductors by : Walter O. Uhoya
Download or read book Phase Transitions and Anomalous Compressibility in 1-2-2 Fe-based Superconductors written by Walter O. Uhoya and published by . This book was released on 2014 with total page 279 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Probing Electroweak Symmetry Breaking at the SSC (Superconducting Super Collider) by :
Download or read book Probing Electroweak Symmetry Breaking at the SSC (Superconducting Super Collider) written by and published by . This book was released on 1987 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Low energy theorems are derived for scattering of longitudinally polarized W and Z's, providing the basis for an estimate of the observable signal at the SSC if electroweak symmetry breaking is due to new physics at the TeV scale.
Book Synopsis Pairing State with a Time-reversal Symmetry Breaking in FeAs-based Superconductors by :
Download or read book Pairing State with a Time-reversal Symmetry Breaking in FeAs-based Superconductors written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We investigate the competition between the extended s± wave and dx2-y2 -wave pairing order parameters in the iron-based superconductors. Because of the frustrating pairing interactions among the electron and the hole fermi pockets, a time-reversal symmetry breaking s + id pairing state could be favored. We analyze this pairing state within the Ginzburg-Landau theory, and explore the experimental consequences. In such a state, spatial inhomogeneity induces supercurrent near a non-magnetic impurity and the corners of a square sample. The resonance mode between the s± and dx2?y2 -wave order parameters can be detected through the B1g-Raman spectroscopy.
Book Synopsis Atomic Structure Design in Iron Based Superconductors by : Jong-Hoon Kang
Download or read book Atomic Structure Design in Iron Based Superconductors written by Jong-Hoon Kang and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Optical Characterization of Time Reversal Symmetry Breaking States in Heavy Fermion Superconductors by : Elizabeth Regina Schemm
Download or read book Optical Characterization of Time Reversal Symmetry Breaking States in Heavy Fermion Superconductors written by Elizabeth Regina Schemm and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Heavy fermion materials have been of interest for decades because of the numerous ordered phases they exhibit at low temperatures, often resulting in novel bulk properties including various forms of magnetic ordering and unconventional superconductivity. A full understanding of these phases and their associated order parameters requires knowledge of their corresponding symmetries. This thesis examines specifically the role of time-reversal symmetry (TRS), as probed by polar Kerr effect (PKE) measurements, in identifying the order parameter of the canonical heavy fermion superconductors UPt_3 and URu_2Si_2. In UPt_3, the onset of PKE is observed below a temperature T_Kerr that coincides with the low temperature "B phase" superconducting transition temperature T_c- ~ 480 mK. In contrast, no change in Kerr effect is observed through either the high temperature "A phase" superconducting transition at T_c+ ~ 550 mK or the small-moment antiferromagnetic (AF) transition at T_N ~ 5 K. These results indicate that TRS is broken only in the B phase, independently of the higher temperature AF order, thus placing strong restrictions on the theory of superconductivity in this system. The case of URu_2Si_2 is more complex. There is a finite PKE loosely associated with the so-called "hidden order" (HO) transition at T_HO ~ 17.5 K. However, the magnitude of the signal appears to depend on the strength of the magnetic field used to train it, and for high fields the signal clearly onsets at ~25 K -- well above T_HO. At lower temperatures, an additional Kerr signal appears below the superconducting transition T_c ~ 1.5 K, which is independent of impurity concentration and which can be trained independently of the HO signal, all of which is consistent with broken TRS intrinsic to superconductivity in \URS. At the same time, an anomaly in the PKE data at ~0.8-1 K is consistently observed whose origins remain a puzzle; there is still more to be learned about URu_2Si_2 within the superconducting state.
Book Synopsis Magnetic Dynamics in Iron-based Superconductors Probed by Neutron Spectroscopy by : Alice Elizabeth Taylor
Download or read book Magnetic Dynamics in Iron-based Superconductors Probed by Neutron Spectroscopy written by Alice Elizabeth Taylor and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Competing Phases in Iron-Based Superconductors Studied by High-Resolution Thermal-Expansion and Shear-Modulus Measurements by : Anna Elisabeth Böhmer
Download or read book Competing Phases in Iron-Based Superconductors Studied by High-Resolution Thermal-Expansion and Shear-Modulus Measurements written by Anna Elisabeth Böhmer and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Interplay of Magnetic, Orthorhombic, and Superconducting Phase Transitions in Iron Based Superconductors by :
Download or read book Interplay of Magnetic, Orthorhombic, and Superconducting Phase Transitions in Iron Based Superconductors written by and published by . This book was released on 2014 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Symmetry with a Twist by : Paul Myles Eugenio
Download or read book Symmetry with a Twist written by Paul Myles Eugenio and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: We utilize crystal symmetry to develop low-energy models for a broad range of superlattice devices composed of stacks of FeSe (and similar iron-based superconductors), with the aim of engineering experimentally tunable couplings through flattening of the superlattice bands.
Book Synopsis Particle-Hole Symmetry Breaking in the Pseudogap State of Bi2201 by :
Download or read book Particle-Hole Symmetry Breaking in the Pseudogap State of Bi2201 written by and published by . This book was released on 2011 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: In conventional superconductors, a gap exists in the energy absorption spectrum only below the transition temperature (T{sub c}), corresponding to the energy price to pay for breaking a Cooper pair of electrons. In high-T{sub c} cuprate superconductors above T{sub c}, an energy gap called the pseudogap exists, and is controversially attributed either to pre-formed superconducting pairs, which would exhibit particle-hole symmetry, or to competing phases which would typically break it. Scanning tunnelling microscopy (STM) studies suggest that the pseudogap stems from lattice translational symmetry breaking and is associated with a different characteristic spectrum for adding or removing electrons (particle-hole asymmetry). However, no signature of either spatial or energy symmetry breaking of the pseudogap has previously been observed by angle-resolved photoemission spectroscopy (ARPES). Here we report ARPES data from Bi2201 which reveals both particle-hole symmetry breaking and dramatic spectral broadening indicative of spatial symmetry breaking without long range order, upon crossing through T* into the pseudogap state. This symmetry breaking is found in the dominant region of the momentum space for the pseudogap, around the so-called anti-node near the Brillouin zone boundary. Our finding supports the STM conclusion that the pseudogap state is a broken-symmetry state that is distinct from homogeneous superconductivity.
