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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Hybridization of Bogoliubov Quasiparticles between Adjacent CuO 2 Layers in the Triple-Layer Cuprate Bi 2 Sr 2 Ca 2 Cu 3 O 10 + δ Studied by Angle-Resolved Photoemission Spectroscopy

Hybridization of Bogoliubov quasiparticles (BQPs) between the CuO 2 layers in the triple-layer cuprate high-temperature superconductor Bi 2 Sr 2 Cu 2 Cu 3 O 10+δ is studied by angle-resolved photoemission spectroscopy (ARPES). In the superconducting state, an anticrossing gap opens between the outer- and inner-BQP bands, which we attribute primarily to interlayer single-particle hopping with possible contributions from interlayer Cooper pairing. We find that the d-wave superconducting gap of both BQP bands smoothly develops with momentum without an abrupt jump in contrast to a previous ARPES study. Hybridization between the BQPs also gradually increases in going from the off nodal to the antinodal region, which is explained by the momentum dependence of the interlayer single-particle hopping. As possible mechanisms for the enhancement of the superconducting transition temperature, the hybridization between the BQPs as well as the combination of phonon modes of the triple CuO 2 layers and spin fluctuations represented by a four-well model are discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Materials preparation, single-crystal growth, and the phase diagram of the cuprate high-temperature superconductor La 1.6-x Nd 0.4 Sr x CuO 4

One branch of the La-214 family of cuprate superconductors, La 1.6-x Nd 0.4 Sr x CuO 4 (NdLSCO), has been of significant and sustained interest, in large part because it displays the full complexity of the phase diagram for canonical hole-doped, high TC superconductivity, while also displaying relatively low superconducting critical temperatures. The low superconducting TC’s imply that experimentally accessible magnetic fields can suppress the superconductivity to zero temperature. In particular, this has enabled various transport and thermodynamic studies of the T = 0 ground state in Nd-LSCO, free of superconductivity, across the critical doping p* = 0.23 where the pseudogap phase ends. The strong dependence of its superconducting properties on its crystal symmetry has itself motivated careful studies of the Nd-LSCO structural phase diagram. This paper provides a systematic study and summary of the materials preparation and characterization of both single crystal and polycrystalline samples of Nd-LSCO. Single-phase polycrystalline samples with x spanning the range from 0.01 to 0.40 have been synthesized, and large single crystals of La 1.6-x Nd 0.4 Sr x CuO 4 for select x across the region (0.07, 0.12, 0.17, 0.19, 0.225, 0.24, and 0.26) were grown by the optical floating zone method. Furthermore, systematic neutron and X-ray diffraction studies on these samples were performed at both low and room temperatures, 10 K and 300 K, respectively. These studies allowed us to follow the various structural phase transitions and propose an updated structural phase diagram for NdLSCO. In particular, we found that the low-temperature tetragonal (LTT) phase ends at a critical doping p LTT = 0.255±0.005, clearly separated from p*.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Structural changes induced by electric currents in a single crystal of Pr 2 CuO 4

We demonstrate an approach to the structural and electronic property modification of perovskites, focusing on Pr 2 CuO 4 , an undoped parent compound of a class of electron-doped copper-oxide superconductors. Currents were passed parallel or perpendicular to the copper oxygen layers with the voltage ramped up until a rapid drop in the resistivity was achieved, a process referred to as “flash.” The current was then further increased tenfold in current-control mode. This state was quenched by immersion into liquid nitrogen. Flash can drive many compounds into different atomic structures with new properties, whereas the quench freezes them into a long-lived state. Single-crystal neutron diffraction of as-grown and modified Pr 2 CuO 4 revealed a √10 ×√10 superlattice due to oxygen-vacancy order. The diffraction peak intensities of the superlattice of the modified sample were significantly enhanced relative to the pristine sample. Raman-active phonons in the modified sample were considerably sharper. Measurements of electrical resistivity, magnetization, and two-magnon Raman scattering indicate that the modification affected only the Pr-O layers, but not the Cu-O planes. These results point to enhanced oxygen-vacancy order in the modified samples well beyond what can be achieved without passing electrical current. Our work opens a new avenue toward electric field/quench control of structure and properties of layered perovskite oxides.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Light-Induced Melting of Competing Stripe Orders without Introducing Superconductivity in La 2 − x Ba x CuO 4

The ultrafast manipulation of quantum material has led to many novel and significant discoveries. Among them, the light-induced transient superconductivity in cuprates achieved by melting competing stripe orders represents a highly appealing accomplishment. However, recent investigations have shown that the notion of photoinduced superconductivity remains a topic of controversy, and its elucidation solely through c -axis time-resolved terahertz spectroscopy remains an arduous task. Here, we measure the in-plane and out-of-plane transient terahertz responses simultaneously in the stripe-ordered nonsuperconducting La 2 − x Ba x CuO 4 after near-infrared excitations. We find that although a pump-induced reflectivity edge appears in the c -axis reflectance spectrum, the reflectivity along the CuO 2 planes decreases simultaneously, indicating an enhancement in the scattering rate of quasiparticles. This in-plane transient response is clearly distinct from the features associated with superconducting condensation. Therefore, we conclude the out-of-plane transient responses cannot be explained by an equivalent of Josephson tunneling. Notably, those pump-induced terahertz responses remain consistent even when we vary the near-infrared optical pump wavelengths and hole concentrations. Our results provide critical evidence that transient three-dimensional superconductivity cannot be induced by melting the competing stripe orders with pump pulses whose photon energy is much higher than the superconducting gap of cuprates. Published by the American Physical Society 2024

36 MATERIALS SCIENCE↗
NASA NTRS1987

Upper critical field of high temperature Y(1.2)Ba(0.8)CuO(4-delta) superconductor

A 20-T high-field magnet is used to measure electrical resistance as a function of temperature in the Y(1.2)Ba(0.8)CuO(4-delta) superconductor. The temperature dependence of the critical field, Hc2(T), is obtained from the superconduction transition. A Hc2(O) value of 166T is determined which is the highest critical field yet reported. Results show Y(1.2)Ba(0.8)CuO(4-delta) to be a 90K Type-II superconductor, with a lower critical field Hc1(O) of about 0.2T and a penetration depth of about 290 A.

Hor, P. H.↗
DOE OSTI2020

Materials Data on CuO by Materials Project

CuO is Halite, Rock Salt structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Cu2+ is bonded to six equivalent O2- atoms to form a mixture of edge and corner-sharing CuO6 octahedra. The corner-sharing octahedral tilt angles are 0°. All Cu–O bond lengths are 2.12 Å. O2- is bonded to six equivalent Cu2+ atoms to form a mixture of edge and corner-sharing OCu6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CuO by Materials Project

CuO crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Cu2+ is bonded in a square co-planar geometry to four equivalent O2- atoms. There is two shorter (1.94 Å) and two longer (1.96 Å) Cu–O bond length. O2- is bonded to four equivalent Cu2+ atoms to form a mixture of edge and corner-sharing OCu4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tl(CuO)2 by Materials Project

Tl(CuO)2 crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. there are two inequivalent Cu+1.50+ sites. In the first Cu+1.50+ site, Cu+1.50+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.98 Å. In the second Cu+1.50+ site, Cu+1.50+ is bonded in a linear geometry to two equivalent O2- atoms. Both Cu–O bond lengths are 1.83 Å. Tl1+ is bonded in an L-shaped geometry to two equivalent O2- atoms. Both Tl–O bond lengths are 2.48 Å. O2- is bonded in a 4-coordinate geometry to three Cu+1.50+ and one Tl1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CuO by Materials Project

CuO crystallizes in the tetragonal P4_2/nmc space group. The structure is three-dimensional. there are two inequivalent Cu2+ sites. In the first Cu2+ site, Cu2+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.83 Å) and one longer (1.84 Å) Cu–O bond length. In the second Cu2+ site, Cu2+ is bonded to five O2- atoms to form distorted edge-sharing CuO5 square pyramids. There are a spread of Cu–O bond distances ranging from 1.89–2.56 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Cu2+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Cu2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CuO by Materials Project

CuO crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Cu2+ sites. In the first Cu2+ site, Cu2+ is bonded in a linear geometry to two O2- atoms. Both Cu–O bond lengths are 1.82 Å. In the second Cu2+ site, Cu2+ is bonded in a 4-coordinate geometry to five O2- atoms. There are a spread of Cu–O bond distances ranging from 1.88–2.56 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Cu2+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to four Cu2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CuO by Materials Project

CuO crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Cu2+ is bonded in a square co-planar geometry to four equivalent O2- atoms. There is two shorter (1.95 Å) and two longer (1.96 Å) Cu–O bond length. O2- is bonded to four equivalent Cu2+ atoms to form a mixture of corner and edge-sharing OCu4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li3(CuO)4 by Materials Project

Li3(CuO)4 crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded to four O2- atoms to form a mixture of distorted edge and corner-sharing LiO4 tetrahedra. There are a spread of Li–O bond distances ranging from 1.92–2.11 Å. In the second Li1+ site, Li1+ is bonded in a distorted see-saw-like geometry to four O2- atoms. There is two shorter (1.95 Å) and two longer (2.04 Å) Li–O bond length. There are two inequivalent Cu+1.25+ sites. In the first Cu+1.25+ site, Cu+1.25+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.84 Å) and one longer (1.87 Å) Cu–O bond length. In the second Cu+1.25+ site, Cu+1.25+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.81 Å) and one longer (1.83 Å) Cu–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to three Li1+ and two Cu+1.25+ atoms to form distorted OLi3Cu2 trigonal bipyramids that share a cornercorner with one OLi4Cu2 octahedra, corners with three equivalent OLi3Cu2 trigonal bipyramids, and edges with two equivalent OLi4Cu2 octahedra. The corner-sharing octahedral tilt angles are 8°. In the second O2- site, O2- is bonded to four Li1+ and two equivalent Cu+1.25+ atoms to form distorted OLi4Cu2 octahedra that share corners with two equivalent OLi4Cu2 octahedra, corners with two equivalent OLi3Cu2 trigonal bipyramids, and edges with four equivalent OLi3Cu2 trigonal bipyramids. The corner-sharing octahedral tilt angles are 35°. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to two equivalent Li1+ and two equivalent Cu+1.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CuO by Materials Project

CuO crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Cu2+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.97 Å. O2- is bonded in a square co-planar geometry to four equivalent Cu2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(CuO)4 by Materials Project

Ba(CuO)4 crystallizes in the tetragonal P4/nbm space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight equivalent O2- atoms. All Ba–O bond lengths are 2.81 Å. There are two inequivalent Cu+1.50+ sites. In the first Cu+1.50+ site, Cu+1.50+ is bonded in a linear geometry to two equivalent O2- atoms. Both Cu–O bond lengths are 1.80 Å. In the second Cu+1.50+ site, Cu+1.50+ is bonded in a linear geometry to two equivalent O2- atoms. Both Cu–O bond lengths are 1.80 Å. O2- is bonded in a distorted water-like geometry to two equivalent Ba2+ and two Cu+1.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Structural Phase Separation and Enhanced Superconductivity in La 1.875 Ba 0.125 CuO 4 Under Uniaxial Strain

Strain engineering has attracted significant attention in recent years due to its capability in tuning lattice and electronic structures of quantum materials. Using moderate uniaxial compressive strain, structural phase separation is induced in the low-temperature phase of x = 1/8 La 2-x Ba x CuO 4 (LBCO) single crystals. These structures are low temperature tetragonal (LTT), low temperature less orthorhombic (LTLO), and a plastically deformed nano-domain structure (PDNS), comprised of few-nanometer-sized orthorhombic domains within an amorphous matrix. These three structures exhibit distinct superconducting behaviors. The volume fraction of the LTT structure is suppressed with increasing strain, while its superconducting transition temperature increases and broadens. The LTLO structure exhibits a sharp superconducting transition above 32 K, which increases up to ≈ 36 K at maximum strain. The PDNS phase exhibits a very broad superconducting transition and persists even after removing the strain. This study illustrates the sensitivity of superconductivity to the structure of the LBCO sample near its stripe instability.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Enhanced stability of Fe-modified CuO-ZnO-ZrO 2 -Al 2 O 3 /HZSM-5 bifunctional catalysts for dimethyl ether synthesis from CO 2 hydrogenation

In this report a series of iron (Fe) modified CuO-ZnO-ZrO 2 -Al 2 O 3 (CZZA) catalysts, with various Fe loadings, were prepared using a co-precipitation method. A bifunctional catalyst, consisting of Fe-modified CZZA and HZSM-5, was studied for dimethyl ether (DME) synthesis via CO 2 hydrogenation. The effects of Fe loading, reaction temperature, reaction pressure, space velocity, and concentrations of precursor for the synthesis of the Fe-modified CZZA catalyst on the catalytic activity of DME synthesis were investigated. Long-term stability tests showed that Fe modification of the CZZA catalyst improved the catalyst stability for DME synthesis via CO 2 hydrogenation. The activity loss, in terms of DME yield, was significantly reduced from 4.2% to 1.4% in a 100 h run of reaction, when the Fe loading amount was 0.5 (molar ratio of Fe to Cu). An analysis of hydrogen temperature programmed reduction revealed that the introduction of Fe improved the reducibility of the catalysts, due to assisted adsorption of H 2 on iron oxide. The good stability of Fe-modified CZZA catalysts in the DME formation was most likely attributed to oxygen spillover that was introduced by the addition of iron oxide. This could have inhibited the oxidation of the Cu surface and enhanced the thermal stability of copper during long-term reactions.

42 ENGINEERING↗
DOE OSTI2023

La$_{2-x}$Ba$_x$CuO$_4$ as a superconducting Rosetta Stone

The high-temperature superconductivity in layered cuprates discovered by Bednorz and Müller arrived as a shock. Gradually, the presence of competing orders, such as antiferromagnetism and charge order, were discovered; however, the relationship to the superconductivity has been confusing. Importantly, it so happens that the original cuprate superconductor family La$_{2-x}$Ba$_x$CuO$_4$ contains all of the relevant phases, with extreme competition among them, and analysis of these phases provides strong clues to the nature of the superconductivity in cuprates.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

On the Development of Order and Interfaces during the Growth of Ultrathin La 2 CuO 4 Films by Molecular Beam Epitaxy

While the atomic structure of interfaces in complex oxide heterostructures created by epitaxial growth has been investigated extensively, few studies have been conducted on how interfaces form and restructure at the initial stage of film growth. The dynamic aspects of the growth behavior can strongly influence the final interfacial atomic structure, which may lead to the emergence of interface-specific properties, such as the rise of interfacial superconductivity between certain Ruddlesden-Popper oxide materials. In this report, the structural development of La2CuO 4 thin films grown by molecular beam epitaxy on a LaSrAlO 4 substrate is investigated by X-ray diffraction measurements with rapid scans over a volume of reciprocal space. This method provides far more detailed information on interface formation than traditional fixed-point measurements. The results show that the atomic structure of the interface becomes fully established after just a single unit cell of growth. Interestingly, restructuring continues to occur within the topmost half to one unit cell of the film during the deposition process. However, diffraction intensity oscillations from both reflection high-energy electron and X-ray measurements stabilize only after the growth of two unit cells, indicating that the growth front morphology continues to evolve until the start of the third unit cell. This multimodal investigation provides insights into the atomic processes taking place during layered oxide interface formation, including the dynamical rearrangement of LaO and CuO 2 layers. Such information is not only relevant to the engineering and optimization of functional layer structures but can also be critical for ultrathin films.

36 MATERIALS SCIENCE↗