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Results for “superconductor electronics”

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.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Effects of electron irradiation on high temperature superconductors and contacts to high temperature superconductors

The discovery of a new class of ceramic superconductors with transition temperatures above liquid nitrogen has opened the doors for exciting space applications. Energy storage, pointing maneuvers, magnetic shielding, and sensitive detection of electromagnetic radiation are some of the longer term possible applications. One near term application involves low electrical resistance, high thermal resistance connections between a detector operating at approximatly or equal to 4 and the electronics operating at approximatly or equal to 77 K. The new high temperature superconductors could accomplish this providing the necessary electrical connections to the ground plane while isolating the system thermally, thus prolonging the life of the mission. With such possibilities it is clearly of value to study the effects of radiation that would be experienced during a typical space mission. In this work we focused specifically on the effects of the electron radiation environment.

Caton, Randall↗
NASA NTRS1992

A comparison of superconductor and manganin technology for electronic links used in space mission applications

The electronic link connecting cryogenically cooled radiation detectors to data acquisition and signal processing electronics at higher temperatures contributes significantly to the total heat load on spacecraft cooling systems that use combined mechanical and cryogenic liquid cooling. Using high transition temperature superconductors for this link has been proposed to increase the lifetime of space missions. Herein, several YBCO (YBa2Cu3O7) superconductor-substrate combinations were examined and total heat loads were compared to manganin wire technology in current use. Using numerical solutions to the heat-flow equations, it is shown that replacing manganin technology with YBCO thick film technology can extend a 7-year mission by up to 1 year.

Caton, R.↗
DOE OSTI2019

Functional form of the superconducting critical temperature from machine learning

Predicting the critical temperature $T_c$ of new superconductors is a notoriously difficult task, even for electron-phonon paired superconductors, for which the theory is relatively well understood. Early attempts to obtain a simple $T_c$ formula consistent with strong-coupling theory, by McMillan and by Allen and Dynes, led to closed-form approximate relations between $T_c$ and various measures of the phonon spectrum and the electron-phonon interaction appearing in Eliashberg theory. Here we propose that these approaches can be improved with the use of machine-learning algorithms. As an initial test, we train a model for identifying low-dimensional descriptors using the $T_c$ < 10 K dataset by Allen and Dynes, and show that a simple analytical expression thus obtained improves upon the Allen-Dynes fit. Furthermore, the prediction for the recently discovered high-$T_c$ material H 3 S at high pressure is quite reasonable. Interestingly, $T_c$'s for more recently discovered superconducting systems with a more two-dimensional electron-phonon coupling, which do not follow Allen and Dynes's expression, also do not follow our analytic expression. Thus, this machine-learning approach appears to be a powerful method for highlighting the need for a new descriptor beyond those used by Allen and Dynes to describe their set of isotropic electron-phonon coupled superconductors. Finally, we argue that this machine-learning method, and its implied need for a descriptor characterizing Fermi-surface properties, represents a promising approach to superconductor materials discovery which may eventually replace the serendipitous discovery paradigm begun by Kamerlingh Onnes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Pervasive electronic nematicity in a cuprate superconductor

Here, we describe an extensive experimental study of La 2-x Sr x CuO 4 films synthesized by molecular beam epitaxy and investigated by angle-resolved measurements of transverse resistivity (without applied magnetic field). The data show that an unusual metallic state, in which the rotational symmetry of the electron fluid is spontaneously broken, occurs in a large temperature and doping region. The superconducting state always emerges out of this nematic metal state.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Electron pairing in high-T(c) superconductors

For Cu-O systems, there may be considerable deviations from conventional antiferromagnetism when E(d)-E(p) is of about 0. When holes are introduced, then these systems may become superconductors because of the attractions between electron pairs.

Tsang, T.↗
DOE OSTI2021

Anharmonic theory of superconductivity in the high-pressure materials

Electron-phonon superconductors at high pressures have displayed the highest values of critical superconducting temperature Tc on record, now rapidly approaching room temperature. Despite the importance of high-P superconductivity in the quest for room-temperature superconductors, a mechanistic understanding of the effect of pressure and its complex interplay with phonon anharmonicity and superconductivity is missing, as numerical simulations can bring only system-specific details, clouding out key players controlling the physics. In this work, we develop a minimal model of electron-phonon superconductivity under an applied pressure which takes into account the anharmonic decoherence of the optical phonons. We find that T c behaves nonmonotonically as a function of the ratio Γ/ω 0 , where Γ is the optical phonon damping and ω 0 is the optical phonon energy at zero pressure and momentum. Optimal pairing occurs for a critical ratio Γ/ω 0 when the phonons are on the verge of decoherence (“diffusonlike” limit). Our framework gives insights into recent experimental observations of T c as a function of pressure in the complex BCS material TlInTe 2 .

36 MATERIALS SCIENCE↗
DOE OSTI2021

Spectral properties and enhanced superconductivity in renormalized Migdal-Eliashberg theory

Migdal-Eliashberg theory describes the properties of the normal and superconducting states of electron-phonon-mediated superconductors based on a perturbative treatment of the electron-phonon interactions. It is necessary to include both electron and phonon self-energies self-consistently in Migdal-Eliashberg theory in order to match numerically exact results from determinantal quantum Monte Carlo in the adiabatic limit. Here in this work we provide a method to obtain the real-axis solutions of the Migdal-Eliashberg equations with electron and phonon self-energies calculated self-consistently. Our method avoids the typical challenge of computing cumbersome singular integrals on the real axis and is numerically stable and exhibits fast convergence. Analyzing the resulting real-frequency spectra and self-energies of the two-dimensional Holstein model, we find that self-consistently including the lowest-order correction to the phonon self-energy significantly affects the solution of the Migdal-Eliashberg equations. The calculation captures the broadness of the spectral function, renormalization of the phonon dispersion, enhanced effective electron-phonon coupling strength, minimal increase in the electron effective mass, and the enhancement of superconductivity which manifests as a superconducting ground state despite strong competition with charge-density-wave order. We discuss surprising differences in two common definitions of the electron-phonon coupling strength derived from the electron mass and the density of states, quantities which are accessible through experiments such as angle-resolved photoemission spectroscopy and electron tunneling. An approximate upper bound on 2Δ/T c for conventional superconductors mediated by retarded electron-phonon interactions is proposed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Raman Spectroscopy of Pnictide and other Unconventional Superconductors

Coupling between electrons in “strongly correlated materials” is associated with many scientifically important and technologically useful phenomena, including unconventional superconductivity, charge, spin or orbital ordered states. Understanding the behavior of novel superconductors presents a great intellectual challenge and is critical to developing new technologies. This work included spectroscopic studies of (1) unconventional superconductors with competing ground states, (2) recently discovered and technologically important superconductors from the iron-pnictide family which demonstrate high transition temperature and high critical fields, and (3) heavy fermion materials which demonstrate exotic ground states.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Charge- 4 e and Charge- 6 e Flux Quantization and Higher Charge Superconductivity in Kagome Superconductor Ring Devices

The flux quantization is a key indication of electron pairing in superconductors. For example, the well-known h / 2 e flux quantization is considered strong evidence for the existence of charge- 2 e , two-electron Cooper pairs. Here we report evidence for multicharge flux quantization in mesoscopic ring devices fabricated using the transition-metal kagome superconductor CsV 3 Sb 5 . We perform systematic magnetotransport measurements and observe unprecedented quantization of magnetic flux in units of h / 4 e and h / 6 e in magnetoresistance oscillations. Specifically, at low temperatures, magnetoresistance oscillations with period h / 2 e are detected, as expected from the flux quantization for charge- 2 e superconductivity. We find that the h / 2 e oscillations are suppressed and replaced by resistance oscillations with h / 4 e periodicity when the temperature is increased. Increasing the temperature further suppresses the h / 4 e oscillations, and robust resistance oscillations with h / 6 e periodicity emerge as evidence for charge- 6 e flux quantization. Our observations provide the first experimental evidence for the existence of multicharge flux quanta and emergent quantum matter exhibiting higher-charge superconductivity in the strongly fluctuating region above the charge- 2 e Cooper pair condensate, revealing new insights into the intertwined and vestigial electronic order in kagome superconductors. Published by the American Physical Society 2024

Physics↗
DOE OSTI2018

Dynamical instability of the electric transport in superconductors

We develop a nonlinear theory of the electronic transport in superconductors in the framework of the time-dependent Ginzburg-Landau (TDGL) equation. We utilize self-consistent Gaussian approximation and reveal the conditions under which the current-voltage V(I) dependence (I-V characteristics) acquires an S-shape form leading to switching instabilities. We demonstrate that in two-dimensions the emergence of such an instability is a hallmark of the Berezinskii-Kosterlitz-Thou less (BKT) transition that we have detected by transport measurements of titanium nitride (TiN) films. Our theoretical findings compare favorably with our experimental results.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

Electron-momentum dependence of electron-phonon coupling underlies dramatic phonon renormalization in YNi 2 B 2 C

Electron-phonon coupling, i.e., the scattering of lattice vibrations by electrons and vice versa, is ubiquitous in solids and can lead to emergent ground states such as superconductivity and charge-density wave order. A broad spectral phonon line shape is often interpreted as a marker of strong electron-phonon coupling associated with Fermi surface nesting, i.e., parallel sections of the Fermi surface connected by the phonon momentum. Alternatively broad phonons are known to arise from strong atomic lattice anharmonicity. Here, we show that strong phonon broadening can occur in the absence of both Fermi surface nesting and lattice anharmonicity, if electron-phonon coupling is strongly enhanced for specific values of electron-momentum, k. We use inelastic neutron scattering, soft x-ray angle-resolved photoemission spectroscopy measurements and ab-initio lattice dynamical and electronic band structure calculations to demonstrate this scenario in the highly anisotropic tetragonal electron-phonon superconductor YNi 2 B 2 C. This new scenario likely applies to a wide range of compounds.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2025

Anisotropic field-induced changes in the superconducting order parameter of UTe 2

UTe 2 is a newly discovered unconventional superconductor, where electron Cooper pairs combine into a spin-triplet ground state. We study the specific heat C( H,T ) of a high-quality UTe 2 single crystal, with a single anomaly at a high superconducting transition temperature T c = 2.1 K and a low residual Sommerfeld coefficient γ 0 . Applying magnetic fields up to 12 T along the crystallographic axes a, b , and c , we observe highly anisotropic behavior in γ 0 ( H ). Below 4 T, γ 0 ( H ) ≈ γ 0 + λi √H (i = a, b, c) , which is expected for an unconventional superconductor with nodes on the Fermi surface away from the direction of the magnetic field. At 4 T ( a and b axes) and 5.5 T ( c axis), distinctive changes in the behavior of γ 0 (H) suggest that a stable low-field ground state begins to evolve above 4 T. The data analysis indicates that the nodes are located near the a–b plane, with possible order parameters d B2u + iεd B1u or d B2u + iεd Au . Our findings support B 2u as the primary superconducting order parameter in UTe 2 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

Fit-free optical determination of electronic thermalization time in nematic iron-based superconductors

We present a nematic response function model (NRFM) for fit-free direct extraction of the characteristic time of ultrafast electronic thermalization in iron-based superconductors, materials with electronic nematicity. By combining the NRFM for polarization-dependent pump–probe measurements of electronic nematic response with the two-temperature model (TTM) for sub-picosecond quasiparticle relaxation, we quantify the electronic thermalization timescales and their anisotropy. The nematic response function is modeled as the difference in normalized reflectivity signals, revealing a pronounced sub-picosecond extremum in signal evolution that directly yields the characteristic electronic thermalization time. This method demonstrates that the NRFM is consistent with TTM fits of transient optical response, yielding electronic thermalization time constants on the order of 110–230 fs for the FeSe 1−x Te x and Ba(Fe 0.92 Co 0.08 ) 2 As 2 thin films. Here, the proposed approach can be applied to any material that exhibits electronic nematicity, providing a powerful tool for direct mapping of the relaxation time in nematic materials, avoiding complex experimental data-fitting procedures.

Bartenev, Alexander [University of Puerto Rico, Ma↗
DOE OSTI2019

Transmission EBSD (t-EBSD) as Tool to Investigate Nanostructures in Superconductors

The transmission electron backscatter diffraction (t-EBSD) technique has proven to be an indispensable tool for the analysis of microstructures of superconducting samples, both high-T{sub c} samples (YBa{sub 2}Cu{sub 3}O{sub y}, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}) as well as MgB{sub 2} or iron-based materials. The knowledge of the grain boundary properties (misorientation, length, width) is essential for the further optimization of sample performance. Any addition of secondary phase(s) to improve the flux pinning properties is required to be of nanometer dimensions, so the higher achievable resolution and the better imaging properties are important to obtain reasonably high image quality to enable automated orientation mapping. The orientation maps reveal not only the location and the shape of the inclusions within the superconducting matrix or at the grain boundaries but also their influence on the surrounding superconducting matrix, which also plays an important role in flux pinning. In the case of sintered MgB{sub 2} bulk samples, the demand for higher critical current densities leads to MgB{sub 2} grains in the 100-nm range, which is already difficult to be studied by means of conventional EBSD. Furthermore, t-EBSD is useful for the analysis of specific microstructures of unconventional superconductors like superconducting foams or superconducting nanowire networks.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Phonon-mediated high-T c superconductivity in hole-doped diamond-like crystalline hydrocarbon

We here predict by ab initio calculations phonon-mediated high-T c superconductivity in hole-doped diamond-like cubic crystalline hydrocarbon K 4 -CH (space group I2 1 /3). This material possesses three key properties: (i) an all-sp 3 covalent carbon framework that produces high-frequency phonon modes, (ii) a steep-rising electronic density of states near the top of the valence band, and (iii) a Fermi level that lies in the σ-band, allowing for a strong coupling with the C-C bond-stretching modes. The simultaneous presence of these properties generates remarkably high superconducting transition temperatures above 80 K at an experimentally accessible hole doping level of only a few percent. These results identify a new extraordinary electron-phonon superconductor and pave the way for further exploration of this novel superconducting covalent metal.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗