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Author: Publisher: ISBN: Category : Languages : en Pages : 5
Book Description
In this study, the concept of intertwined orders has been introduced to describe the cooperative relationship between antiferromagnetic spin correlations and electron (or hole) pair correlations that develop in copper-oxide superconductors. This contrasts with systems in which, for example, charge-density-wave (CDW) order competes for Fermi surface area with superconductivity. La2-xBaxCuO4 with x = 0.125 provides an example in which the ordering of spin stripes coincides with the onset of two-dimensional superconducting correlations. The apparent frustration of the interlayer Josephson coupling has motivated the concept of the pair-density-wave superconductor, a state that theoretical calculations show to be energetically competitive with the uniform d-wave superconductor. Even at x = 0.095, where there is robust superconductivity below 32 K in zero field, the coexistence of strong, low-energy, incommensurate spin excitations implies a spatially modulated and intertwined pair wave function. Recent observations of CDW order in YBa2Cu3O6+x and other cuprate families have raised interesting questions regarding the general role of charge modulations and the relation to superconductivity. While there are differences in the doping dependence of the modulation wave vectors in YBa2Cu3O6+x and La2-xBaxCuO4, the maximum ordering strength is peaked at the hole concentration of 1/8 in both cases. There are also possible connections with the quantum oscillations that have been detected about the same hole concentration but at high magnetic fields. Resolving these relationships remains a research challenge.
Author: Publisher: ISBN: Category : Languages : en Pages : 5
Book Description
In this study, the concept of intertwined orders has been introduced to describe the cooperative relationship between antiferromagnetic spin correlations and electron (or hole) pair correlations that develop in copper-oxide superconductors. This contrasts with systems in which, for example, charge-density-wave (CDW) order competes for Fermi surface area with superconductivity. La2-xBaxCuO4 with x = 0.125 provides an example in which the ordering of spin stripes coincides with the onset of two-dimensional superconducting correlations. The apparent frustration of the interlayer Josephson coupling has motivated the concept of the pair-density-wave superconductor, a state that theoretical calculations show to be energetically competitive with the uniform d-wave superconductor. Even at x = 0.095, where there is robust superconductivity below 32 K in zero field, the coexistence of strong, low-energy, incommensurate spin excitations implies a spatially modulated and intertwined pair wave function. Recent observations of CDW order in YBa2Cu3O6+x and other cuprate families have raised interesting questions regarding the general role of charge modulations and the relation to superconductivity. While there are differences in the doping dependence of the modulation wave vectors in YBa2Cu3O6+x and La2-xBaxCuO4, the maximum ordering strength is peaked at the hole concentration of 1/8 in both cases. There are also possible connections with the quantum oscillations that have been detected about the same hole concentration but at high magnetic fields. Resolving these relationships remains a research challenge.
Author: Publisher: ISBN: Category : Languages : en Pages : 26
Book Description
The electronic phase diagrams of many highly correlated systems, and in particular the cuprate high temperature superconductors, are complex, with many different phases appearing with similar--sometimes identical--ordering temperatures even as material properties, such as a dopant concentration, are varied over wide ranges. This complexity is sometimes referred to as "competing orders." However, since the relation is intimate, and can even lead to the existence of new phases of matter such as the putative "pair-density-wave," the general relation is better thought of in terms of "intertwined orders." We selectively analyze some of the experiments in the cuprates which suggest that essential aspects of the physics are reflected in the intertwining of multiple orders--not just in the nature of each order by itself. We also summarize and critique several theoretical ideas concerning the origin and implications of this complexity.
Author: Edwin Wang Huang Publisher: ISBN: Category : Languages : en Pages :
Book Description
Strongly correlated quantum materials are of interest for both their exotic phases, often harboring multiple intertwined orders, and their unconventional normal states. This thesis investigates these topics from the perspective of numerical simulations of strongly correlated toy model Hamiltonians. First, I present large scale determinantal quantum Monte Carlo calculations demonstrating fluctuating spin stripes in both the Emery and Hubbard models on a 2d square lattice. These results suggest the pervasiveness and importance of density wave ordering in the phase diagram of high-Tc cuprate superconductors. Furthermore, they shed new light on interpreting previous numerical results for the Hubbard model. Second, I discuss transport properties of the 2d Hubbard model evaluated by analytic continuation of DQMC data. Our data, extending to temperatures around an order of magnitude below the Fermi temperature, show features reminiscent of the strange metal phase observed in unconventional superconductors, including resistivity with linear-T dependence and in violation of the Mott-Ioffe-Regel limit. I conclude with a survey of possible ideas that might enable one to go beyond the results in this thesis.
Author: Martin Bluschke Publisher: Springer Nature ISBN: 3030479021 Category : Science Languages : en Pages : 170
Book Description
In this thesis chemical and epitaxial degrees of freedom are used to manipulate charge and spin ordering phenomena in two families of transition metal oxides, while taking advantage of state-of-the-art resonant x-ray scattering (RXS) methods to characterize their microscopic origin in a comprehensive manner. First, the relationship of charge density wave order to both magnetism and the "pseudogap" phenomenon is systematically examined as a function of charge-carrier doping and isovalent chemical substitution in single crystals of a copper oxide high-temperature superconductor. Then, in copper oxide thin films, an unusual three-dimensionally long-range-ordered charge density wave state is discovered, which persists to much higher temperatures than charge-ordered states in other high-temperature superconductors. By combining crystallographic and spectroscopic measurements, the origin of this phenomenon is traced to the epitaxial relationship with the underlying substrate. This discovery opens new perspectives for the investigation of charge order and its influence on the electronic properties of the cuprates. In a separate set of RXS experiments on superlattices with alternating nickel and dysprosium oxides, several temperature- and magnetic-field-induced magnetic phase transitions are discovered. These observations are explained in a model based on transfer of magnetic order and magneto-crystalline anisotropy between the Ni and Dy subsystems, thus establishing a novel model system for the interplay between transition-metal and rare-earth magnetism.
Author: Yvonne Kung Publisher: ISBN: Category : Languages : en Pages :
Book Description
Strongly correlated electron systems exhibit a panoply of fascinating phases, such as antiferromagnetism, charge order, and unconventional superconductivity, that compete or cooperate with one another. Yet the intertwined degrees of freedom that create this complexity also obscure the underlying mechanisms, so that numerous experimental and theoretical studies have been brought to bear on these materials. This thesis provides a window on the field from the perspective of phenomenological and microscopic studies of the cuprates and nickelates. The first part presents a phenomenological model of strongly coupled orders that explains recent time-resolved x-ray diffraction experiments on the nickelates. The new experimental technique enables us to disentangle degrees of freedom that are intertwined in thermal equilibrium, motivating a need for theoretical developments. Our time-dependent Ginzburg-Landau theory facilitates an understanding of how coupled orders behave when driven out of equilibrium. The second part of the thesis explores numerical simulations of microscopic models to answer open questions in the cuprates. A comparison of spin and charge susceptibilities computed in the single-band Hubbard model via determinant quantum Monte Carlo (DQMC) to those calculated using the random phase approximation (RPA) elucidates how electronic correlations evolve throughout the phase diagram. Combined DQMC and exact diagonalization (ED) studies of the three-orbital Hubbard model systematically evaluate broken-symmetry states that have been proposed to explain the pseudogap regime. Thus the use of complementary techniques, both analytical and computational, sheds light on different ordered phases and excitations in strongly correlated systems and points the way to further studies.
Author: Andrew Achkar Publisher: ISBN: Category : Languages : en Pages : 178
Book Description
Cuprate high temperature superconductors have been the subject of intense investigation since their discovery in 1986. The nature of the pairing mechanism in these unconventional superconductors does not seem to be mediated by phonons, as in conventional superconductors, and thus remains a puzzle. The superconducting phase emerges from doping holes (or electrons) into the copper oxide planes of an anti-ferromagnetic Mott insulator, producing a wealth of electronic ordering phenomena in many of the cuprate families. One of these phases is an incommensurate charge ordered state, known since the mid 90's to occur in La-based cuprates along with incommensurate spin ordering and compete with superconductivity. Recent advances in experimental capabilities, notably the ability to perform resonant diffraction experiments with soft x-rays, which can be made sensitive to holes in Cu 3d and O 2p orbitals, have provided new opportunities to learn about these charge ordered states. The study of charge order in cuprate superconductors by resonant soft x-ray scattering is the subject of this thesis.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
The appearance of spin-density-wave (SDW) magnetic order in the low-temperature and high-field corner of the superconducting phase diagram of CeCoIn5 is unique among unconventional superconductors. The nature of this magnetic $Q$ phase is a matter of current debate. Here, we present the thermal conductivity of CeCoIn5 in a rotating magnetic field, which reveals the presence of an additional order inside the $Q$ phase that is intimately intertwined with the superconducting d-wave and SDW orders. A discontinuous change of the thermal conductivity within the $Q$ phase, when the magnetic field is rotated about antinodes of the superconducting d-wave order parameter, demands that the additional order must change abruptly, together with the recently observed switching of the SDW. Lastly, a combination of interactions, where spin-orbit coupling orients the SDW, which then selects the secondary p -wave pair-density-wave component (with an average amplitude of 20% of the primary d-wave order parameter), accounts for the observed behavior.
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Author: Edwin Wang Huang
Author: Martin Bluschke
Author: David Robert Hamilton
Author: Yvonne Kung
Author: Andrew Achkar
Author: Erez Berg
Author: Ying Zhang
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