Showing papers on "High-temperature superconductivity published in 2013"
TL;DR: The phase diagram for an FeSe monolayer grown on a SrTiO3 substrate is reported, by tuning the charge carrier concentration over a wide range through an extensive annealing procedure, and strong indications of superconductivity are observed with a transition temperature of 65±5 K.
Abstract: The recent discovery of possible high-temperature superconductivity in single-layer FeSe films has generated significant experimental and theoretical interest. In both the cuprate and the iron-based high-temperature superconductors, superconductivity is induced by doping charge carriers into the parent compound to suppress the antiferromagnetic state. It is therefore important to establish whether the superconductivity observed in the single-layer sheets of FeSe--the essential building blocks of the Fe-based superconductors--is realized by undergoing a similar transition. Here we report the phase diagram for an FeSe monolayer grown on a SrTiO3 substrate, by tuning the charge carrier concentration over a wide range through an extensive annealing procedure. We identify two distinct phases that compete during the annealing process: the electronic structure of the phase at low doping (N phase) bears a clear resemblance to the antiferromagnetic parent compound of the Fe-based superconductors, whereas the superconducting phase (S phase) emerges with the increase in doping and the suppression of the N phase. By optimizing the carrier concentration, we observe strong indications of superconductivity with a transition temperature of 65±5 K. The wide tunability of the system across different phases makes the FeSe monolayer ideal for investigating not only the physics of superconductivity, but also for studying novel quantum phenomena more generally.
713 citations
TL;DR: In this paper, the spin density wave (SDW) in FeSe films was investigated and the authors showed that the superconductivity occurs when the electrons transferred from the oxygen-vacant substrate suppress the otherwise most pronounced SDW in single layer FeSe.
Abstract: The record of superconducting transition temperature(Tc) has long been 56K for the iron-based high temperature superconductors(Fe-HTS's). Recently, in single layer FeSe films grown on SrTiO3 substrate, signs for a new 65K Tc record are reported. Here with in-situ photoemission measurements, we substantiate the presence of the spin density wave(SDW) in FeSe films, a key ingredient of Fe-HTS that was missed in FeSe before, which weakens with increased thickness or reduced strain. We demonstrate that the superconductivity occurs when the electrons transferred from the oxygen-vacant substrate suppress the otherwise most pronounced SDW in single layer FeSe. Besides providing a comprehensive understanding of FeSe films and directions to further enhance its Tc, we establish the phase diagram of FeSe vs. lattice constant that contains all the essential physics of Fe-HTS's. With the simplest structure, cleanest composition and single tuning parameter, it is ideal for testing theories of Fe-HTS's.
416 citations
Journal Article•
TL;DR: It is proposed that (electron-)doping Sr(2)IrO(4) can potentially realize high-temperature superconductivity and derive several simple facts based on this mapping and the known results about the Hubbard model and the cuprates.
251 citations
TL;DR: It is demonstrated that the iron superconductors, without most of the drawbacks of the cuprates, have a superior high-field performance over low-temperaturesuperconductors at 4.2 K.
Abstract: Although high-temperature superconductor cuprates have been discovered for more than 25 years, superconductors for high-field application are still based on low-temperature superconductors, such as Nb3Sn. The high anisotropies, brittle textures and high manufacturing costs limit the applicability of the cuprates. Here we demonstrate that the iron superconductors, without most of the drawbacks of the cuprates, have a superior high-field performance over low-temperature superconductors at 4.2 K. With a CeO2 buffer, critical current densities >106 A cm−2 were observed in iron-chalcogenide FeSe0.5Te0.5 films grown on single-crystalline and coated conductor substrates. These films are capable of carrying critical current densities exceeding 105 A cm−2 under 30 tesla magnetic fields, which are much higher than those of low-temperature superconductors. High critical current densities, low magnetic field anisotropies and relatively strong grain coupling make iron-chalcogenide-coated conductors particularly attractive for high-field applications at liquid helium temperatures. Iron-based superconductors have the potential to carry higher currents and withstand higher magnetic fields than present-day superconducting cables. Using an approach developed for cuprates, Si et al. improve the high-field performance of iron-based superconductors well beyond that of conventional superconductors.
226 citations
TL;DR: This work demonstrates for the quintessential compound HgBa2CuO4+δ a dramatic switch from linear to purely quadratic (Fermi liquid-like, ρ ∝ T2) resistive behavior in the pseudogap regime and reveals the fundamental resistance per copper–oxygen sheet.
Abstract: Upon introducing charge carriers into the copper–oxygen sheets of the enigmatic lamellar cuprates, the ground state evolves from an insulator to a superconductor and eventually to a seemingly conventional metal (a Fermi liquid). Much has remained elusive about the nature of this evolution and about the peculiar metallic state at intermediate hole-carrier concentrations (p). The planar resistivity of this unconventional metal exhibits a linear temperature dependence (ρ ∝ T) that is disrupted upon cooling toward the superconducting state by the opening of a partial gap (the pseudogap) on the Fermi surface. Here, we first demonstrate for the quintessential compound HgBa2CuO4+δ a dramatic switch from linear to purely quadratic (Fermi liquid-like, ρ ∝ T2) resistive behavior in the pseudogap regime. Despite the considerable variation in crystal structures and disorder among different compounds, our result together with prior work gives insight into the p-T phase diagram and reveals the fundamental resistance per copper–oxygen sheet in both linear (ρ☐ = A1☐T) and quadratic (ρ☐ = A2☐T2) regimes, with A1☐ ∝ A2☐ ∝ 1/p. Theoretical models can now be benchmarked against this remarkably simple universal behavior. Deviations from this underlying behavior can be expected to lead to new insight into the nonuniversal features exhibited by certain compounds.
174 citations
TL;DR: In this paper, a topological insulator on top of a high-temperature superconducting substrate is proposed to induce superconductivity in the surface states of the topological topology.
Abstract: By growing a topological insulator on top of a high-temperature superconducting substrate it is possible to induce superconductivity in the surface states of the topological insulator. Moreover, the pairing symmetry of the induced superconductivity is s-wave, unlike the d-wave symmetry of the substrate.
150 citations
TL;DR: In this paper, the authors reported appearance of superconductivity at 5'K in NdO0.5F 0.5BiS2 and supplement the discovery of the same in layered sulfide based compound.
Abstract: We report appearance of superconductivity at 5 K in NdO0.5F0.5BiS2 and supplement the discovery [Demura et al., e-print arXiv:1207.5248] of the same in layered sulfide based compound. Detailed structural analysis showed that the studied compound is crystallized in tetragonal P4/nmm space group with lattice parameters a = 3.9911(3) A and c = 13.3830(2) A. Bulk superconductivity is established in NdO0.5F0.5BiS2 at 5 K by both transport and magnetic measurements. Electrical transport measurements showed superconducting Tc onset at 5.2 K and Tc (ρ = 0) at 4.7 K. Under applied magnetic field, both Tc onset and Tc (ρ = 0) decrease to lower temperatures and an upper critical field [Hc2(0)] of above 23 kOe is estimated. Isothermal magnetization exhibited typical type-II behavior with lower critical field (Hc1) of around 25 Oe. Specific heat [Cp(T)] is investigated in the temperature range of 1.9–50 K in zero external magnetic field. A Schottky-type anomaly is observed at low temperature below 7 K.
94 citations
TL;DR: It is suggested that high-Tc superconductivity in iron pnictides is associated with both the presence of high-energy spin excitations and a coupling between low-energy spins and itinerant electrons.
Abstract: High-temperature superconductivity in iron pnictides occurs when electrons and holes are doped into their antiferromagnetic parent compounds. Since spin excitations may be responsible for electron pairing and superconductivity, it is important to determine their electron/hole-doping evolution and connection with superconductivity. Here we use inelastic neutron scattering to show that while electron doping to the antiferromagnetic BaFe2As2 parent compound modifies the low-energy spin excitations and their correlation with superconductivity ( 100meV), hole-doping suppresses the high-energy spin excitations and shifts the magnetic spectral weight to low-energies. In addition, our absolute spin susceptibility measurements for the optimally hole-doped iron pnictide reveal that the change in magnetic exchange energy below and above Tc can account for the superconducting condensation energy. These results suggest that high-Tc superconductivity in iron pnictides is associated with both the presence of high-energy spin excitations and a coupling between low-energy spin excitations and itinerant electrons.
90 citations
TL;DR: In this article, the differences between the measured and calculated electronic band structures look insignificant, but can be crucial for understanding of the mechanism of high temperature superconductivity in iron-based superconductors.
Abstract: ARPES experiments on iron based superconductors show that the differences between the measured and calculated electronic band structures look insignificant, but can be crucial for understanding of the mechanism of high temperature superconductivity. Here, we focus on those differences for 111 and 122 compounds and discuss the observed correlation of the experimental band structure with the superconductivity.
46 citations
TL;DR: In this paper, the spin fluctuations and the symmetries of the superconducting gaps for different iron-based superconductors are studied. And the authors argue that the spin fluctuation is the common origin of superconductivity.
Abstract: In this article, we review the recent theoretical works on the spin fluctuations and superconductivity in iron-based superconductors. Using the fluctuation exchange approximation and multi-orbital tight-binding models, we study the characteristics of the spin fluctuations and the symmetries of the superconducting gaps for different iron-based superconductors. We explore the systems with both electron-like and hole-like Fermi surfaces (FS) and the systems with only the electron-like FS. We argue that the spin-fluctuation theories are successful in explaining at least the essential part of the problems, indicating that the spin fluctuation is the common origin of superconductivity in iron-based superconductors.
43 citations
TL;DR: It is shown, using angle-resolved photoemission spectroscopy, that the Fermi liquid quasiparticle excitations of the overdoped superconducting cuprate La1.77Sr0.23CuO4 is highly anisotropic in momentum space and hence the Kadowaki-Wood's relation is not obeyed.
Abstract: High-temperature superconductivity emerges from an un-conventional metallic state. This has stimulated strong efforts to understand exactly how Fermi liquids breakdown and evolve into an un-conventional metal. A fundamental question is how Fermi liquid quasiparticle excitations break down in momentum space. Here we show, using angle-resolved photoemission spectroscopy, that the Fermi liquid quasiparticle excitations of the overdoped superconducting cuprate La1.77Sr0.23CuO4 is highly anisotropic in momentum space. The quasiparticle scattering and residue behave differently along the Fermi surface and hence the Kadowaki-Wood's relation is not obeyed. This kind of Fermi liquid breakdown may apply to a wide range of strongly correlated metal systems where spin fluctuations are present.
TL;DR: In this paper, the electronic structure of the majority of the known stoichiometric inorganic compounds, as listed in the Inorganic Crystal Structure Data-base (ICSD), is compared with the calculated over 60,000 electronic structures.
TL;DR: In this paper, the relationship between the cold-work deformation process and the superconducting properties of the wires was systematically studied and it was found that flat rolling can efficiently increase the mass density of the core, thus, significantly improving the transport critical current density (Jc) of the drawn wires.
Abstract: Seven-core Ag/Fe sheathed Sr0.6K0.4Fe2As2 (Sr-122) superconducting wires were produced by the ex situ powder-in-tube method. The relationship between the cold-work deformation process and the superconducting properties of the wires was systematically studied. It was found that flat rolling can efficiently increase the mass density of the superconducting core, thus, significantly improving the transport critical current density (Jc) of the as-drawn wires. The transport Jc of the best sample achieved 21.1 kA/cm2 at 4.2 K in self field, and showed very weak magnetic field dependence at high fields. Our result suggested a promising future of multifilamentary iron-based superconductors in practical applications.
14 Aug 2013
TL;DR: In this paper, the authors describe the early challenges in correlated electron physics and describe the experimental picture provided by a variety of spectroscopic and transport techniques, and discuss how it is used to determine spin correlations, especially in model systems of quantum magnetism.
Abstract: One of the major themes in correlated electron physics over the last quarter century has been the problem of high-temperature superconductivity in hole-doped copper-oxide compounds. Fundamental to this problem is the competition between antiferromagnetic spin correlations, a symptom of strong Coulomb interactions, and the kinetic energy of the doped carriers, which favors delocalization. After discussing some of the early challenges in the field, I describe the experimental picture provided by a variety of spectroscopic and transport techniques. Then I turn to the technique of neutron scattering, and discuss how it is used to determine spin correlations, especially in model systems of quantum magnetism. Neutron scattering and complementary techniques have determined the extent to which antiferromagnetic spin correlations survive in the cuprate superconductors. One experimental case involves the ordering of spin and charge stripes. I first consider related measurements on model compounds, such as La2−xSrxN...
TL;DR: In this paper, a novel family of thallium halide-based compounds are proposed as candidates for new high temperature superconductors, whose superconductivity is mediated by the recently proposed mechanism of non-local correlationenhanced strong electron-phonon coupling.
Abstract: We design, from first principles calculations, a novel family of thallium halide-based compounds as candidates for new high temperature superconductors, whose superconductivity is mediated by the recently proposed mechanism of non-local correlation-enhanced strong electron-phonon coupling. Two prototype compounds namely CsTlF$_3$ and CsTlCl$_3$ are studied with various hole doping levels and volumes. The critical superconducting temperature T$_c$ are predicted to be about 30 K and 20 K with $\sim$0.35/f.u. hole doping and require only modest pressures ($\sim$10 and $\sim$2 GPa), respectively. Our procedure of designing this class of superconductors is quite general and can be used to search for other "other high temperature superconductors".
TL;DR: In this paper, the authors explore the cuprate phase diagram by electronic Raman spectroscopy and shed light on the superconducting state in hole-doped curates, namely, how superconductivity and the critical temperature Tc are affected by the pseudogap.
Abstract: The mechanism of unconventional superconductivity is still unknown despite over 25 years passing since the discovery of high-Tc cuprate superconductors by Bednorz and Muller (1986 Z. Phys. B 64 189). Here, we explore the cuprate phase diagram by electronic Raman spectroscopy and shed light on the superconducting state in hole-doped curates, namely, how superconductivity and the critical temperature Tc are affected by the pseudogap.
TL;DR: In this paper, the authors investigated the amplitude and frequency dependence of AC susceptibility of sol-gel synthesized polycrystalline samples of Bi 2 Sr 2 CaCu 2 O 8+ δ (Bi-2212) sintered at different temperatures.
TL;DR: In this article, experimental designs suitable to test pairing symmetry in multiband Fe-based superconductors are proposed, which are based on combinations of tunnel junctions and point contacts and should be accessible by existing sample fabrication techniques.
Abstract: We suggest experimental designs suitable to test pairing symmetry in multiband Fe-based superconductors. These designs are based on combinations of tunnel junctions and point contacts and should be accessible by existing sample fabrication techniques.
TL;DR: In this paper, the authors investigated the properties of superconductivity in correlated-electron systems by using numerical methods such as the variational Monte Carlo method and the quantum Monte Carlomethod.
Abstract: We present recent theoretical results on superconductivity in correlated-electron systems, especially in the two-dimensional Hubbard model and the three-band d-p model. The mechanism of superconductivity in high-temperature superconductors has been extensively studied on the basis of various electronic models and also electron-phonon models. In this study, we investigate the properties of superconductivity in correlated-electron systems by using numerical methods such as the variational Monte Carlo method and the quantum Monte Carlomethod. The Hubbard model is one of basic models for strongly correlated electron systems, and is regarded as the model of cuprate high temperature superconductors. The d-p model is more realistic model for cuprates. The superconducting condensation energy obtained by adopting the Gutzwiller ansatz is in reasonable agreement with the condensation energy estimated for YBa2Cu3O7. We show the phase diagram of the ground state using this method. We have further investigated the stability of striped and checkerboard states in the under-doped region. Holes doped in a half-filled square lattice lead to an incommensurate spin and charge density wave. The relationship of the hole density x and incommensurability δ, δ~x, is satisfied in the lower doping region, as indicated by the variationalMonte Carlocalculations for the two-dimensional Hubbard model. A checkerboard-like charge-density modulation with a roughly period has also been observed by scanning tunneling microscopy experiments in Bi2212 and Na-CCOC compounds. We have performed a variational Monte Carlo simulation on a two-dimensional t-t′-t″- U Hubbard model with a Bi-2212 type band structure and found that the period checkerboard spin modulation, that is characterized by multi Q vectors, is indeed stabilized. We have further performed an investigation by using a quantumMonte Carlomethod, which is a numerical method that can be used to simulate the behavior of correlated electron systems. We present a new algorithm of the quantum Monte Carlo diagonalization that is a method for the evaluation of expectation value without the negative sign problem. We compute pair correlation functions and show that pair correlation is indeed enhanced with hole doping.
TL;DR: In this article, angle-resolved photoemission spectroscopy experiments on overdoped cuprate high temperature superconductors were performed to test the relationship between the superconducting transition temperature and electron-bosonic mode coupling.
Abstract: Electronic band dispersions in copper oxide superconductors have kinks around 70 meV that are typically attributed to coupling of electrons to a bosonic mode. We performed angle-resolved photoemission spectroscopy experiments on overdoped cuprate high temperature superconductors to test the relationship between the superconducting transition temperature and electron-bosonic mode coupling. Remarkably, the kinks remain strong in the heavily overdoped region of the doping phase diagram of La${}_{2\ensuremath{-}x}$Sr${}_{x}$CuO${}_{4}$, even when the superconductivity completely disappears. This unexpected observation is incompatible with the conventional picture of superconductivity mediated by the sharp bosonic modes that are responsible for the kink unless extra doping strongly suppresses their $d$-wave projection but not the overall spectral weight. Our results favor pairing mediated by a very broad electronic spectrum or an unconventional mechanism without pairing glue.
TL;DR: In this article, the effect of CuO intergrowths on the superconductivity of bilayer La2/3Ca1/3MnO3/YBa2Cu3O7−δ (LCMO/YBCO) thin-film heterostructures was examined.
Abstract: We examine the effect of CuO intergrowths on the superconductivity in epitaxial La2/3Ca1/3MnO3/YBa2Cu3O7−δ (LCMO/YBCO) thin-film heterostructures. Scanning transmission electron microscopy on bilayer LCMO/YBCO thin films revealed double CuO-chain intergrowths which form regions with the 247 lattice structure in the YBCO layer. These nanoscale 247 regions do not appear in x-ray diffraction, but can physically account for the reduced critical temperature (Tc) of bilayer thin films relative to unilayer films with the same YBCO thickness, at least down to ∼25 nm. We attribute the CuO intergrowths to the bilayer heteroepitaxial mismatch and the Tc reduction to the generally lower Tc seen in bulk 247 samples. These epitaxially-induced CuO intergrowths provide a microstructural mechanism for the attenuation of superconductivity in LCMO/YBCO heterostructures.
TL;DR: Findings point to a surface-enhanced incipient charge-density-wave instability, driven by Fermi surface nesting, which establishes the surface of cuprates and other complex oxides as a rich playground for the study of electronically soft phases.
Abstract: As well as superconductivity, cuprate perovskites can exhibit many different exotic spin and charge ordering states. Adding to this, Rosen et al. identify a stark difference in the electronic structure of the cuprate Bi2201 between its surface and its bulk.
TL;DR: In this article, the surface properties of co-doped BaFe2As2 epitaxial superconducting thin films were inspected by X-ray photoelectron spectroscopy, scanning spreading resistance microscopy (SSRM), and point contact Spectroscopy (PCS).
Abstract: Surface properties of Co-doped BaFe2As2 epitaxial superconducting thin films were inspected by X-ray photoelectron spectroscopy, scanning spreading resistance microscopy (SSRM), and point contact spectroscopy (PCS). It has been shown that surface of Fe-based superconductors degrades rapidly if being exposed to air, what results in suppression of gap-like structure on PCS spectra. Moreover, SSRM measurements revealed inhomogeneous surface conductivity, what is consistent with strong dependence of PCS spectra on contact position. Presented results suggest that fresh surface and small probing area should be assured for surface sensitive measurements like PCS to obtain intrinsic properties of Fe-based superconductors.
17 Jul 2013
TL;DR: In this article, the shape resonance of a superconductor made of multiple condensates is tuned to shape resonance in superconducting gaps and the maximum Tc occurs where the puddles form scale free superconding networks.
Abstract: A characteristic feature of a superconductor made of multiple condensates is the possibility of the shape resonances in superconducting gaps. Shape resonances belong to class of Fano resonances in configuration interaction between open and closed scattering channels. The Shape resonances arise because of the exchange interaction, a Josephson-like term, for transfer of pairs between different condensates in different Fermi surface spots in the special cases where at least one Fermi surface is near a 2.5 Lifshitz topological transition. We show that tuning the shape resonances show first, the gap suppression (like a Fano anti-resonance) driven by configuration interaction between a BCS condensate and a BEC-like condensate, and second, the gap amplification (like a Fano resonance) driven by configuration interaction between BCS condensates in large and small Fermi surfaces. Shape resonances usually occur in granular nanoscale complex matter (called superstripes) because of the lattice instability near a 2.5 Lifshitz transition in presence of interactions. Using a new imaging method, scanning nano-X-ray diffraction, we have shown the generic formation in high temperature superconductors of a granular superconducting networks made of striped puddles formed by ordered oxygen interstitials or ordered local lattice distortions (like static short range charge density waves). In the superconducting puddles the chemical potential is tuned to a shape resonance in superconducting gaps and the maximum Tc occurs where the puddles form scale free superconducting networks.
TL;DR: In this article, pressure-induced elimination of long-ranged antiferromagnetic (AFM) order at 34 GPa and a crossover from an AFM insulating to a metallic state at 20 GPa in LaMnPO single crystals that are iso-structural to the LaFeAsO superconductor were reported.
Abstract: The emergence of superconductivity in the iron pnictide or cuprate high temperature superconductors usually accompanies the suppression of a long-ranged antiferromagnetic (AFM) order state in a corresponding parent compound by doping or pressurizing. A great deal of effort by doping has been made to find superconductivity in Mn-based compounds, which are thought to bridge the gap between the two families of high temperature superconductors, but the AFM order was not successfully suppressed. Here we report the first observations of the pressure-induced elimination of long-ranged AFM order at ~ 34 GPa and a crossover from an AFM insulating to an AFM metallic state at ~ 20 GPa in LaMnPO single crystals that are iso-structural to the LaFeAsO superconductor by in-situ high pressure resistance and ac susceptibility measurements. These findings are of importance to explore potential superconductivity in Mn-based compounds and to shed new light on the underlying mechanism of high temperature superconductivity.
TL;DR: In this paper, the application of magneto-optical imaging (MOI) to key superconducting materials suitable for the hydrogen economy: MgB2 and high temperature superconductors in bulk and thin-film form.
Abstract: Restricted deposits of fossil fuels and ecological problems created by their extensive use require a transition to renewable energy resources and clean fuel free from emissions of CO2 This fuel is likely to be liquid hydrogen An important feature of liquid hydrogen is that it allows wide use of superconductivity Superconductors provide compactness, high efficiency, savings in energy and a range of new applications not possible with other materials The benefits of superconductivity justify use of low temperatures and facilitate development of fossil-free energy economy The widespread use of superconductors requires a simple and reliable technique to monitor their properties Magneto-optical imaging (MOI) is currently the only direct technique allowing visualization of the superconducting properties of materials We report the application of this technique to key superconducting materials suitable for the hydrogen economy: MgB2 and high temperature superconductors (HTS) in bulk and thin-film form The study shows that the MOI technique is well suited to the study of these materials It demonstrates the advantage of HTS at liquid hydrogen temperatures and emphasizes the benefits of MgB2, in particular
TL;DR: In this paper, the first ever practical-level field generation for an undulator consisting of bulk high-temperature superconductors is reported and described, which enables bright hard X-ray to be obtained in moderate-energy synchrotrons and to provide a polarized MeV gamma-ray source for producing a polarized positron beam via pair production in future linear colliders.
Abstract: The first ever practical-level field generation for an undulator consisting of bulk high-temperature superconductors is reported and described. A high-field short-period undulator enables bright hard X-ray to be obtained in moderate-energy synchrotrons and to provide a polarized MeV gamma-ray source for producing a polarized positron beam via pair production in future linear colliders. To generate sinusoidal magnetic fields using bulk high-temperature superconductors, a novel structure has been developed in which the superconductors line up in a staggered configuration inside a solenoid. An undulator field of 0.85 T is achieved using a 10 mm period, 4 mm gap prototype in a 2 T solenoid.
TL;DR: In this article, evidence for high Tc cuprate superconductivity is found in a region of the phase diagram where non-superconducting Fermi liquid metals are expected.
Abstract: Evidence for high-Tc cuprate superconductivity is found in a region of the phase diagram where non-superconducting Fermi liquid metals are expected. Cu valences estimated independently from both x-ray absorption near-edge spectroscopy and bond valence sum measurements are >2.3, and are in close agreement with each other for structures in the homologous series (Cu0.75Mo0.25)Sr2(Y,Ce)sCu2O5+2s+δ with s = 1, 2, 3, and 4. The record short apical oxygen distance, at odds with current theory, suggests the possibility of a new pairing mechanism. The possibility that the charge reservoir layers are able to screen long range coulomb interactions and thus enhance Tc is discussed.
TL;DR: In this paper, a theoretical analysis of current transport in the [001]-tilt low angle grain boundary according to the strain energy of dislocation is presented, and an analytical expression is obtained which has the similar form of the fitting function, and in which the physical characteristics of parameters are distinct, and their values are close to the reports in literature.
Abstract: Current transport in grain boundary is one of the crucial factors which can affect the macro-supercurrent characteristics of the high temperature superconductors. van der Laan et al. [Phys. Rev. Lett. 103, 027005 (2009)] presented the strain dependence of the critical current density with a power-law fitting function, which has been verified by many experimental measurements. Here, we present a theoretical analysis of current transport in the [001]-tilt low angle grain boundary according to the strain energy of dislocation. An analytical expression is obtained which has the similar form of the fitting function, and in which the physical characteristics of parameters are distinct, and their values are close to the reports in literature.
Posted Content•
TL;DR: In this article, the authors reported the first observation of the pressure-induced elimination of long-ranged AFM order in LaMnPO single crystals that are iso-structural to the LaFeAsO superconductor.
Abstract: The emergence of superconductivity in the iron pnictide and cuprate high temperature superconductors usually accompanies the suppression of an antiferromagnetically (AFM) ordered state in a corresponding parent compound through the use of chemical doping or external pressure1-5. A great deal of effort has been made to find superconductivity in Mn-based compounds6-14, which are thought to bridge the gap between the two families of high temperature superconductors7,15,16, but long-ranged AFM order was not successfully suppressed via chemical doping in these investigations. Here we report the first observation of the pressure-induced elimination of long-ranged AFM order in LaMnPO single crystals that are iso-structural to the LaFeAsO superconductor15,17. By combining in-situ high pressure resistance and ac susceptibility measurements, we found that LaMnPO undergoes a crossover from an AFM insulating to an AFM metallic state at a pressure ~20 GPa and that the long-ranged AFM order collapses at a higher pressure ~32 GPa. Our findings are of importance to explore potential superconductivity in Mn-based compounds and to shed new light on the underlying mechanism of high temperature superconductivity.