Calculation of an Enhanced A_{1g} Symmetry Mode Induced by Higgs Oscillations in the Raman Spectrum of High-Temperature Cuprate Superconductors.

In superconductors the Anderson-Higgs mechanism allows for the existence of a collective amplitude (Higgs) mode which can couple to eV light mainly in a nonlinear Raman-like process. The experimental nonequilibrium results on isotropic superconductors have been explained going beyond the BCS theory including the Higgs mode. Furthermore, in anisotropic d-wave superconductors strong interaction effects with other modes are expected. Here we calculate the Raman contribution of the Higgs mode from a new perspective, including many-body Higgs oscillations effects and their consequences in conventional, spontaneous Raman spectroscopy. Our results suggest a significant contribution to the intensity of the A_{1g} symmetry Raman spectrum in d-wave superconductors. In order to test our theory, we predict the presence of measurable characteristic oscillations in THz quench-optical probe time-dependent reflectivity experiments.

Classification and characterization of nonequilibrium Higgs modes in unconventional superconductors.

Recent findings of new Higgs modes in unconventional superconductors require a classification and characterization of the modes allowed by nontrivial gap symmetry. Here we develop a theory for a tailored nonequilibrium quantum quench to excite all possible oscillation symmetries of a superconducting condensate. We show that both a finite momentum transfer and quench symmetry allow for an identification of the resulting Higgs oscillations. These serve as a fingerprint for the ground state gap symmetry. We provide a classification scheme of these oscillations and the quench symmetry based on group theory for the underlying lattice point group. For characterization, analytic calculations as well as full scale numeric simulations of the transient optical response resulting from an excitation by a realistic laser pulse are performed. Our classification of Higgs oscillations allows us to distinguish between different symmetries of the superconducting condensate.

Direct penetration of spin-triplet superconductivity into a ferromagnet in Au/SrRuO3/Sr2RuO4 junctions.

Efforts have been ongoing to establish superconducting spintronics utilizing ferromagnet/superconductor heterostructures. Previously reported devices are based on spin-singlet superconductors (SSCs), where the spin degree of freedom is lost. Spin-polarized supercurrent induction in ferromagnetic metals (FMs) is achieved even with SSCs, but only with the aid of interfacial complex magnetic structures, which severely affect information imprinted to the electron spin. Use of spin-triplet superconductors (TSCs) with spin-polarizable Cooper pairs potentially overcomes this difficulty and further leads to novel functionalities. Here, we report spin-triplet superconductivity induction into a FM SrRuO3 from a leading TSC candidate Sr2RuO4, by fabricating microscopic devices using an epitaxial SrRuO3/Sr2RuO4 hybrid. The differential conductance, exhibiting Andreev-reflection features with multiple energy scales up to around half tesla, indicates the penetration of superconductivity over a considerable distance of 15 nm across the SrRuO3 layer without help of interfacial complex magnetism. This demonstrates potential utility of FM/TSC devices for superspintronics.

Coupling of Higgs and Leggett modes in non-equilibrium superconductors.

In equilibrium systems amplitude and phase collective modes are decoupled, as they are mutually orthogonal excitations. The direct detection of these Higgs and Leggett collective modes by linear-response measurements is not possible, because they do not couple directly to the electromagnetic field. In this work, using numerical exact simulations we show for the case of two-gap superconductors, that optical pump-probe experiments excite both Higgs and Leggett modes out of equilibrium. We find that this non-adiabatic excitation process introduces a strong interaction between the collective modes, which is absent in equilibrium. Moreover, we propose a type of pump-probe experiment, which allows to probe and coherently control the Higgs and Leggett modes, and thus the order parameter directly. These findings go beyond two-band superconductors and apply to general collective modes in quantum materials.

Feedback effect on high-energy magnetic fluctuations in the model high-temperature superconductor HgBa2CuO(4+δ) observed by electronic Raman scattering.

We use electronic Raman scattering to study the model single-layer cuprate superconductor HgBa(2)CuO(4+δ). In an overdoped sample, we observe a pronounced amplitude enhancement of a high-energy peak related to two-magnon excitations in insulating cuprates upon cooling below the critical temperature T(c). This effect is accompanied by the appearance of the superconducting gap and a pairing peak above the gap in the Raman spectrum, and it can be understood as a hitherto-undetected feedback effect on the high-energy magnetic fluctuations due to the Cooper pairing interaction. This implies a direct involvement of the high-energy magnetic fluctuations in the pairing mechanism. All of these effects occur already above T(c) in two underdoped samples, demonstrating a related feedback mechanism associated with the pseudogap.

Two-component dynamics of the order parameter of high temperature Bi2Sr2CaCu2O8+delta superconductors revealed by time-resolved Raman scattering.

We study the dynamics of the superconducting order parameter in the high-Tc cuprate Bi2Sr2CaCu2O8+delta by employing a novel time-resolved pump-probe Raman experiment. We find two different coupling mechanisms that contribute equally to the pair-breaking peak. One coupling sets in very fast at 2 ps and relaxes slowly, while the other one is delayed and sets in roughly at 5 ps and relaxes fast. A model that couples holes through phonons is able to reproduce one part of the condensate dynamics; thus, we argue that hole-spin interactions are of importance as well.

Fermi-liquid-based theory for the in-plane magnetic anisotropy in untwinned high-Tc superconductors.

Using a generalized RPA-type theory we calculate the in-plane anisotropy of the magnetic excitations in hole-doped high-Tc superconductors. Extending our earlier Fermi-liquid-based studies on the resonance peak by inclusion of orthorhombicity we still find two-dimensional spin excitations, however, being strongly anisotropic. This reflects the underlying anisotropy of the hopping matrix elements and of the resultant superconducting gap function. We compare our calculations with new experimental data on fully untwinned YBa2Cu3O6.85 and find good agreement. Our results are in contrast to earlier interpretations on the in-plane anisotropy in terms of stripes [H. Mook, Nature (London) 404, 729 (2000)], but reveal a conventional solution to this important problem.

A hidden pseudogap under the 'dome' of superconductivity in electron-doped high-temperature superconductors.

The ground state of superconductors is characterized by the long-range order of condensed Cooper pairs: this is the only order present in conventional superconductors. The high-transition-temperature (high-T(c)) superconductors, in contrast, exhibit more complex phase behaviour, which might indicate the presence of other competing ground states. For example, the pseudogap--a suppression of the accessible electronic states at the Fermi level in the normal state of high-T(c) superconductors-has been interpreted as either a precursor to superconductivity or as tracer of a nearby ground state that can be separated from the superconducting state by a quantum critical point. Here we report the existence of a second order parameter hidden within the superconducting phase of the underdoped (electron-doped) high-T(c) superconductor Pr2-xCe(x)CuO4-y and the newly synthesized electron-doped material La2-xCe(x)CuO4-y (ref. 8). The existence of a pseudogap when superconductivity is suppressed excludes precursor superconductivity as its origin. Our observation is consistent with the presence of a (quantum) phase transition at T = 0, which may be a key to understanding high-T(c) superconductivity. This supports the picture that the physics of high-T(c) superconductors is determined by the interplay between competing and coexisting ground states.

Analysis of the elementary excitations in high-T(c) cuprates: explanation of the new energy scale observed by angle-resolved photoemission spectroscopy.

We analyze the energy and momentum dependence of the elementary excitations in high- T(c) superconductors resulting from the coupling to spin fluctuations. As a result of the energy dependence of the self-energy Sigma(k,omega), characteristic features occur in the spectral density explaining the "kink" in recent angle-resolved photoemission spectroscopy experiments. We present results for the spectral density A(k,omega) for the feedback of superconductivity on the excitations, and for the superconducting order parameter Delta(k,omega). These results relate also to inelastic neutron scattering and tunneling experiments and shed important light on the essential ingredients a theory of the elementary excitations in the cuprates must contain.

Displaced fractures of the scaphoid.

The scaphoid is the most commonly fractured carpal bone. The displaced fracture poses a particular surgical problem. While scaphoid fractures as a group show a 90%-95% union rate, those fractures with greater than 1 mm of displacement are associated with a 55% incidence of nonunion and a 50% rate of avascular necrosis. Displaced fractures that unite spontaneously do so only after prolonged immobilization and are associated with a greater incidence of painful malunion. Displaced scaphoid fractures that result in malunion or nonunion are more prone to develop late carpal osteoarthritis. The higher incidence of complications with the displaced scaphoid fracture suggests that an anatomic reduction is essential. If closed manipulation is unsuccessful, open reduction and internal fixation are indicated.

Efficacy of bone staples for fixation.

The pull-out strength of two types of bone staples (A, Techmedica; B, Richards) was evaluated in a canine model and compared with a control of 6.5 mm cancellous bone screw (Synthes). Fifteen adult mongrel dogs were divided into three groups of five animals each. The implants were placed in the lateral femoral condyle and proximal humerus on the right side at time zero, and on the left side 3 weeks later. The dogs were killed at 6 weeks. In addition a third site, the tibial tubercle, was used to examine the effectiveness of each device for patellar tendon reattachment. The strength of the reattached patellar tendon was measured and compared with a control intact patellar tendon insertion. The pull-out loads from bone of the two staple types are not statistically different. The displacement to failure, however, was found to be 71% greater (p less than 0.007), and the work to failure 128% greater (p less than 0.010) for staple A as compared with staple B. This may be of clinical relevance in avoiding staple back-out. Both staples were inferior to the screw for pull-out load displacement and work to failure (p less than 0.0001). All reattached tendons were significantly weaker (mean 202 N) than the intact tendon (mean 1,448 N) regardless of implant type. The dissected specimens uniformly showed necrosis of the tendon under the implant. Healing was by massive scar formation surrounding the implant.

The evaluation of a biphasic calcium phosphate ceramic for use in grafting long-bone diaphyseal defects.

The effectiveness of a sintered hydroxyapatite-tricalcium phosphate (HA-TCP) ceramic in bridging large diaphyseal defects in the canine ulna was studied. One-hundred percent morselized HA-TCP, a 50:50 mixture of morselized HA-TCP, and autogenous cancellous bone, and 100% autogenous cancellous bone were used to bridge 2.5-cm defects in the left ulnae of three groups of six dogs each. At 24 weeks the ulnae were explanted and studied by radiography, microradiography, mechanical testing, and histology. Pure HA/TCP was not osteoinductive, and four of six ulnae in this group progressed to a fibrous nonunion. The HA/TCP-cancellous bone mixture and pure cancellous bone were approximately equal in effect, leading to good callus formation at 4 weeks and strong bony union by 24 weeks, with no evidence of bioincompatibility. Morselized HA/TCP promises to be useful as a graft extender when mixed with autogenous cancellous bone.

The operative treatment of mid-shaft clavicular non-unions.

Ten consecutive patients with clavicular non-union were treated at the University of California, Davis, Medical Center and Kaiser Permanente Hospital, Sacramento, with compression-plating and iliac bone-grafting. Seven patients were male and three were female, and their ages ranged from sixteen to sixty years. All patients achieved clinical union by ten weeks postoperatively, with no operative or postoperative complications, and had a full, painless range of motion of the ipsilateral shoulder, with an acceptable cosmetic result. In our experience, patients with symptomatic clavicular non-union may be treated by open reduction and internal fixation with a compression plate and supplemental iliac-bone graft with a high likelihood of success.

Pesticide, metal, and other chemical residues in adult total diet samples. (XIII). August 1976-September 1977.

Since 1964, the Food and Drug Administration has reported residues of pesticides and other chemicals in the average diet of the United States' heartiest eater, the young adult male, through the Total Diet Study. This report is the thirteenth in the series and includes results of analyses for 25 market basket samples collected from August 1976 through September 1977 in 20 different cities throughout 4 geographical areas. All food items were divided into 12 different composite food classes, and 25 composites, 1 from each market basket, were prepared and analyzed for each food class. Averages and ranges of pesticide and chemical residues are presented in various formats, together with results for the following heavy metals: zinc, cadmium, lead, mercury, arsenic, and selenium. Individual items making up the dairy composites and the meat-fish-poultry composites were analyzed separately for 4 market baskets and are presented as a part of this report. Recovery studies of pesticides and chemicals added to each of the various food classes are also included.

Pesticide, heavy metal, and other chemical residues in infant and toddler total diet samples. (III). August 1976-September 1977.

The Total Diet Study has been conducted by the Food and Drug Administration, U.S. Department of Health and Human Services, since 1964 to monitor the diet of adults, and more recently the infant and toddler diet, for residues of pesticides and other chemicals. This report presents the residues found in 12 infant and toddler market baskets, i.e., items comprising the average 2-week diet of infants and toddlers, collected in 12 major cities in 4 geographical areas from August 1976 through September 1977. The analyses for each market basket were performed on composites of each of 11 food classes, and the results are presented in a variety of formats. In addition to chemical residues, the market baskets were also analyzed for 6 heavy metals: arsenic, lead, selenium, zinc, cadmium, and mercury. Results of recovery studies conducted with residue compounds of various types are also included in this report. The results for the adult market baskets for the same period are published as a separate report.

Pesticide, metal, and other chemical residues in adult total diet samples--(XII)--August 1975-July 1976.

This report is on the twelfth in the series on the presence of pesticide and other chemical residues in the average diet of the United States' heartiest eater, the young adult male. Twenty market baskets were collected in 20 U.S. cities that ranged in population from less than 50,000 to 1 million or more. Composites of 12 food classes were analyzed. Averages and ranges of residues found are reported for August 1975 through July 1976, by food class. In addition to the pesticide and chemical residues, data for lead, cadmium, selenium, mercury, arsenic, and zinc are included. The individual items making up the dairy and meat composites in four market baskets were analyzed separately for pesticide residues, and the results are included. Results of recovery studies of pesticides and chemicals within various food classes are also presented.