Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Superconductivity”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

3D superconducting radio-frequency resonators for quantum computing

Superconducting radiofrequency (SRF) technology is being used not only in discovery science programs and basic research but also for several applications that benefit society more directly. The advantage of superconducting resonators over those made of normal-conducting metal is their ability to store electromagnetic energy with much lower dissipation. The high quality factor and longer dissipation time provided by these superconducting resonators can deliver superior performance. Currently, the quantum processing architecture uses resonators and interconnecting circuits operating in the microwave regime with superconducting strip-line technology and low noise electronic devices for switching and communication. The performance of these devices can be enhanced by embedding them in 3D SRF cavity resonators to prolong the coherence time, which improves the utility of the device by reducing error rates and allowing more manipulations (calculations) before the quantum state decays. In this presentation, I will review the current technology and progress towards the three dimensional SRF cavities to enhance the coherence time.

Dhakal, Pashupati↗
DOE OSTI2023

Exploration of Potential Superconducting Multi-Mode Cavity Architectures for Quantum Computing

This thesis describes the investigation of superconducting multi-mode cavity architecture for superconducting transmon-based quantum computing. The dissertation highlights useful features of radio-frequency cavities used for quantum computing, with a brief discussion on the advantages of superconducting cavities. In the subsequent section, the concept of transmon is introduced and the mechanism of coupling with a cavity is analyzed. Once the foundations of the topic are laid down, the thesis focuses on optimizing a multi-mode superconducting rf cavity design originally developed for high-energy physics applications. Such section articulates in two main parts, the first part concerning the "bare" cavity remake via finite-elements eigenmode simulations using a computer-aided design software called CST Studio Suite®. In the second part, a transmon qubit is physically inserted into the modified cavity to assess the qubit-cavity coupling of the new design. In evaluating said coupling, two distinct analysis methods are used, namely the black-box quantization method and the energy participation ratio method, both implemented using Ansys® High-Frequency Electromagnetic-Field Simulator, or HFSS™. Results from the two evaluations, compared together, show that the optimized design meets the requisites to be used for quantum computing purposes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Non‐Fermi‐Liquid Behavior of Superconducting SnH 4

Abstract The chemical interaction of Sn with H 2 by X‐ray diffraction methods at pressures of 180–210 GPa is studied. A previously unknown tetrahydride SnH 4 with a cubic structure ( fcc ) exhibiting superconducting properties below T C = 72 K is obtained; the formation of a high molecular C 2/ m ‐SnH 14 superhydride and several lower hydrides, fcc SnH 2 , and C 2‐Sn 12 H 18 , is also detected. The temperature dependence of critical current density J C (T) in SnH 4 yields the superconducting gap 2Δ(0) = 21.6 meV at 180 GPa. SnH 4 has unusual behavior in strong magnetic fields: B,T ‐linear dependences of magnetoresistance and the upper critical magnetic field B C2 (T) ∝ ( T C – T ). The latter contradicts the Wertheimer–Helfand–Hohenberg model developed for conventional superconductors. Along with this, the temperature dependence of electrical resistance of fcc SnH 4 in non‐superconducting state exhibits a deviation from what is expected for phonon‐mediated scattering described by the Bloch‐Grüneisen model and is beyond the framework of the Fermi liquid theory. Such anomalies occur for many superhydrides, making them much closer to cuprates than previously believed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Origin of Suppression of Proximity-Induced Superconductivity in Bi/Bi 2 Sr 2 CaCu 2 O 8+δ Heterostructures

Mixing of topological states with superconductivity could result in topological superconductivity with the elusive Majorana fermions potentially applicable in fault-tolerant quantum computing. One possible candidate considered for realization of topological superconductivity is thin bismuth films on Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212). Here, we present angle-resolved and core-level photoemission spectroscopy studies of thin Bi films grown in-situ on as-grown Bi2212 that show the absence of proximity effect. We find that the electron transfer from the film to the substrate and the resulting severe underdoping of Bi2212 at the interface is a likely origin for the absence of proximity effect. We also propose a possible way of preventing a total loss of proximity effect in this system. Our results offer a better and more universal understanding of the film/cuprate interface and resolve many issues related to the proximity effect.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Synthesis and Characterization of MoNb Films Superconducting at 100-200 mK

We have developed a new transition-edge sensor material with critical temperature (T-c) in the range 100-200 mK. The new material is a solid solution of two superconducting components, MoxNb1-x, co-sputtered from two high-purity single-component targets (Mo and Nb). The T-c has a minimum (dT(c)/dx = 0) at an intermediate concentration of the components. We have optimized the deposition parameters and composition to provide films with a sharp superconducting transition at ~ 150 mK. We investigated structural features of the films and surface morphology using X-ray diffraction (XRD) and scanning electron microscopy. The XRD measurements indicate that the grown films are polycrystalline, with a preferred orientation along the (110) crystal direction and a clear correlation between superconducting properties and film microstructure.

superconducting alloys↗
DOE OSTI2018

Published Tunneling Results of Binnig et al Interpreted as Related to Surface Superconductivity in SrTiO{sub 3}

In 1980, Binnig et al. reported tunneling measurements on Nb-doped SrTiO{sub 3}, and interpreted their results as indicating two-band superconductivity in the bulk of SrTiO{sub 3}. However, (1) effective masses determined from tunneling results in the normal state by Sroubek in 1969 and 1970 are much smaller than those determined by most other methods. The much smaller masses were attributed to properties of a surface layer by the present author in 1971. (2) The only other reports of two-band superconductivity in bulk SrTiO{sub 3} can be used to infer much smaller values for the band separations than found by Binnig et al. In this paper, we give an alternative explanation of the results of Binnig et al. in terms of superconductivity in a surface layer. We obtain fair fits to the band gaps versus Fermi energy for the two bands in the three samples where two surface subbands are occupied and to the temperature dependence of the gaps in one crystal, using a model with three adjustable interaction parameters, an adjustable energy for the phonons which dominate the pairing, and an adjustable ratio of the mean-field T{sub c} to the actual T{sub c}. We show results for a combined fit to the low-temperature band gaps and to the T-dependence in one crystal. The phonon energy which gives the best fit is 21 meV. This is probably an appropriate average over the three longitudinal polar modes and acoustic modes in the material. A large value of about two is found for the ratio T{sub cmf}/T{sub c}, and we conjecture that this arises because a band with a small Fermi energy, not seen in the tunneling results, plays a part in increasing T{sub cmf}/T{sub c}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of Yb Substitution on Microstructure and Superconducting Properties of Y{sub 1−x}Yb{sub x}Ba{sub 2}Cu{sub 3}O{sub 7−δ} Films

The purpose of this study was to improve the critical current density (J{sub c}) of YBa{sub 2}Cu{sub 3}O{sub 7−δ} (YBCO) superconducting films at high magnetic fields. Thin Y{sub 1−x}Yb{sub x}Ba{sub 2}Cu{sub 3}O{sub 7−δ} (Y{sub 1−x}Yb{sub x}BCO) superconducting films on LaAlO{sub 3} substrates were prepared by modified low-fluorine metal organic deposition method (LF-MOD) in order to investigate the effect of Yb substitution on the microstructure and superconducting properties of a YBCO-coated conductor. In this study, single-phased, c-axial-aligned Y{sub 1−x}Yb{sub x}BCO films were obtained. Yb doping had a little effect on the critical temperature (T{sub c}) and transition width (ΔT) values of Y{sub 1−x}Yb{sub x}BCO films. An abnormal phenomenon was observed that the J{sub c} of Y{sub 1−x}Yb{sub x}BCO films at low field was smaller than that of the pure YBCO film, but the J{sub c} of Y{sub 1−x}Yb{sub x}BCO films at high field was much greater than that of the undoped YBCO film. Compared to pure YBCO film, the J{sub c} values of Y{sub 0.75}Yb{sub 0.25}BCO and Y{sub 0.25}Yb{sub 0.75}BCO films were enhanced by a factor of 8 at 8 T, 65 K, which meant that chemical substitution of Yb into the Y site could improve flux pinning significantly under the high magnetic field in Y{sub 1−x}Yb{sub x}BCO coated conductors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Surface Superconductivity in Ni{sub 50}Mn{sub 36}Sn{sub 14} Heusler Alloy

The changes in the magnetizations of Ni{sub 50}Mn{sub 36}Sn{sub 14} Heusler alloy (L{sub 21}-NiMnSn-HA) with an antiferromagnetic interfacial exchange coupling have been investigated by using the effective field theory as a function of temperature and external magnetic field. It is shown that the Ni component is antiferromagnetic and its other components are ferromagnetic while the L{sub 21}-NiMnSn-HA has a ferrimagnetic ordering below T{sub C}. And, they are paramagnetic above T{sub C}. The L{sub 21}-NiMnSn-HA and its Ni component have the triple hysteresis loops below T* and the other components have only single hysteresis loop below T{sub C}. It is found that they exhibit type II/1 superconductivity at higher external magnetic field below T* and type II/2 superconductivity at lower external magnetic field above T*. Moreover, it is suggested that the surface superconductivity emerges below the conversion temperature of T{sup ∗}≈ 0.74 and can be associated with the triple hysteresis loops which occur in the systems with an antiferromagnetic interfacial exchange coupling. And, the vortex state terminates at T{sub V} ≈ 4.37 for the Ni component of the L{sub 21}-NiMnSn-HA. The H{sub C}-T phase diagrams of the L{sub 21}-NiMnSn-HA and its Ni component are in qualitatively good agreement with the experimental and theoretical findings.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Short Note on Superconductivity at Ambient Temperature and Pressure in Silver-Embedded Gold Nano-particles: a Goldsmith Job Ahead

Very recent observation of superconductivity (arXiv: 1807.08572 ) in both transport (resistance versus temperature) and magnetization (zero field cooled) at around 235 K and above has obviously raised many eyebrows. The experimentalists in particular are more thrilled than the theoreticians. Although the results presented in the paper are clean and both transport and magnetization measurements do approve the observation of superconductivity to some extent (the diamagnetic shielding fraction is low), the problem is to synthesize/fabricate the material. This I called the “goldsmith” job, primarily because one has to deal with gold and silver nano-particle combination/amalgamation/alloying or even who knows the interfacial new phase, which could be superconducting. This short note is written to let the spark continues, and the interesting work of Thapa and Pandey (arXiv: 1807.08572 ) is reproduced independently.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Improvement in the Crystallographic Phase Content and Superconducting Properties of Mechanically Alloyed MgB{sub 2}

In this paper, the results of the superconductivity evaluation of MgB{sub 2} intermetallic-based superconducting materials prepared through mechanical alloying are reported. The formation of the MgB{sub 2} intermetallic phase took place through an intermediate phase reaction at the solid-state reaction temperature, which tends to favor single-phase materials. The annealing of mechanically milled Mg and B powders resulted in the highest mass fraction of MgB{sub 2} observed in this study, reaching more than 90% after annealing at 900 °C for 1 h. At that point, there were still second phases present consisting of Mg, MgO, and Fe{sub 2}B. Improved superconducting properties were obtained in samples sintered at temperatures of 850 °C and 900 °C that had a low resistivity, low critical temperature gap values, and a high residual resistivity ratio (RRR).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Phase-Slip Lines in Wide Superconducting Strips: Charge and Spin Relaxation Lengths

Penetration of spin-polarized charges from a nearby ferromagnetic metallic layer into 100-μm-wide superconducting films of Pb and Mo–Re alloy with similar critical parameters but quite different spin-orbit coupling strengths is studied. It is shown that the diffusion of magnetic properties into a nearby superconductor can be employed as an electrically tunable source of phase-slip events manifesting itself by a staircase response in current-voltage characteristics of the superconductor with discrete metastable resistivity states. Unlike for normal metals, the spin injection into an adjoining quasi-two-dimensional superconducting strip creates not only spin but also charge imbalance in the quasiparticle population which are not necessarily relaxing over the same time scale. Interplay of the two intrinsic length scales sets the width of a phase-slip line in superconducting strips under the injection which may change from nano- to micro-scales. Its experimental determination can be used for estimating the longest relaxation length in a superconductor. Our observations show that spin-orbit coupling in superconductors may lead to novel non-trivial effects linking spin and charge degrees of freedom.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Electronic Structure, Lattice Dynamics, and Superconducting Properties of Mercury-Alkaline Earth Metal Compounds: a First-Principles Study

The electronic structure, lattice dynamics, and superconducting properties of SrHg and BaHg intermetallic compounds are investigated using plane wave pseudo-potential and linear response methods based on density functional theory. The ground state properties such as lattice parameters are in good agreement with previously reported results. The positive phonon frequencies reveal the stability of both compounds in B{sub 2} (CsCl-type) structure. The metallic nature of SrHg and BaHg is confirmed by the electronic band structure as well as phonon dispersion curves. The superconducting behavior described in terms of Eliashberg spectral function (α{sup 2}F(ω)) and electron-phonon coupling constant (λ). The calculated values of superconducting transition temperatures (T{sub c}) show good agreement with available experimental data.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Fate of superconductivity in three-dimensional disordered Luttinger semimetals

Superconducting instability can occur in three-dimensional quadratic band crossing semimetals only at a finite coupling strength due to the vanishing of density of states at the quadratic band touching point. Since realistic materials are always disordered to some extent, we study the effect of short-ranged-correlated disorder on this superconducting quantum critical point using a controlled loop-expansion applying dimensional regularization. The renormalization group (RG) scheme allows us to determine the RG flows of the various interaction strengths and shows that disorder destroys the superconducting quantum critical point. In fact, the system exhibits a runaway flow to strong disorder.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

SuperScreen: An open-source package for simulating the magnetic response of two-dimensional superconducting devices

Quantitative understanding of the spatial distribution of magnetic fields and Meissner screening currents in two-dimensional (2D) superconductors and mesoscopic thin film superconducting devices is critical to interpreting the results of magnetic measurements of such systems. Here, we introduce SuperScreen, an open-source Python package for simulating the response of 2D superconductors to trapped flux and applied time-independent or quasi-DC magnetic fields for any value of the effective magnetic penetration depth, Λ. Given an applied magnetic field, SuperScreen solves the 2D London equation using an efficient matrix inversion method to obtain the Meissner currents and magnetic fields in and around structures composed of one or more superconducting thin films of arbitrary geometry. Further, SuperScreen can be used to model screening effects and calculate self- and mutual-inductance in thin film superconducting devices.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Superconductivity in the presence of disorder in skutterudite-related La 3 Co 4 Sn 13 and La 3 Ru 4 Sn 13 compounds: Electrical transport and magnetic studies

La 3 Co 4 Sn 13 and La 3 Ru 4 Sn 13 were categorized as BCS superconductors. In a plot of the critical field H c2 vs T, La 3 Ru 4 Sn 13 displays a second superconducting phase at the higher critical temperature T c *, characteristic of inhomogeneous superconductors, while La 3 Co 4 Sn 13 shows bulk superconductivity below T c . We observe a decrease in critical temperatures with external pressure and magnetic field for both compounds. Additionally, for La 3 Ru 4 Sn 13 we find that T c */dP>dT c /dP. The pressure dependences of T c are interpreted according to the McMillan theory and understood to be a consequence of lattice stiffening. The investigation of the superconducting state of La 3 Co x Ru 4–x Sn 13 shows a T c * that is larger then T c for x < 4. Furthermore, this unique and unexpected observation is discussed as a result of the local disorder and/or the effect of chemical pressure when Ru atoms are partially replaced by smaller Co atoms.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Superconductivity in alkaline earth metal doped boron hydrides

Effects of alkaline earth metal atoms doping in boron hydrides at high pressure are investigated by first-principles calculations. The calculated results showed that doping with Mg, Ca, Ba, and Sr in B8H16 at 50 GPa is thermodynamically favorable and dynamically stable. The doping changes the B 8 H 16 from a semiconductor to a metal with substantial electronic density-of-state around the Fermi level. The superconductivity of the alkaline earth metal doped B 8 H 16 is studied based on electron-phonon coupling mechanism. The calculated critical superconducting transition temperatures (T c ) range from 10 to 25 K at 50 GPa upon doping. These results suggest that doping metal atoms in boron hydrides is an efficient way in designing superconducting materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Superconductivity in layered BiS 2 -based compounds

Here, a novel family of superconductors based on BiS 2 -based superconducting layers were discovered in 2012. In short order, other BiS 2 -based superconductors with the same or related crystal structures were discovered with superconducting critical temperatures T c of up to 10 K. Many experimental and theoretical studies have been carried out with the goal of establishing the basic properties of these new materials and understanding the underlying mechanism for superconductivity. In this selective review of the literature, we distill the central discoveries from this extensive body of work, and discuss the results from different types of experiments on these materials within the context of theoretical concepts and models.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Predicting the superconducting critical temperature in transition metal carbides and nitrides using machine learning

Transition metal carbides and nitrides have unique mechanical and chemical characteristics. At low temperatures many of them also exhibit superconductivity, which can be controlled by substitutions into both the transition metal and carbon/nitrogen sites. To investigate the factors governing the superconducting state, we apply machine learning methods. Here we collected a dataset containing 147 materials, which was used to create a pipeline for predicting their superconducting critical temperature. When this pipeline is applied to a randomly selected test set, it shows a good performance, with of 0.82 and RMSE of 1.9 K. To explore the limits of the machine learning approach, we also use it to predict entire substitution series within the dataset. This represents a realistic test for the predictive models, which can be extremely useful when applied to new substitutions in materials systems. The performance of the pipeline in this case is much more uneven, with good predictions for some series, while for others the model shows minimal predictive power. We discuss possible reasons for these results, as well as methods to estimate the performance of machine learning on new substitution series.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗