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Results for “applied 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.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Center for Applied Physics and Superconducting Technologies (CAPST)

Fermi Research Alliance, LLC, as operator of Fermi National Accelerator Laboratory (Fermilab) and Northwestern University (Northwestern) have a broad overlap in scientific interests and complementary state-of-the-art facilities in the area of applied physics and technology, in particular physics of superconductivity, materials science, and detector technology. The Center for Applied Physics and Superconducting Technology (CAPST) will provide a mechanism for cross-utilizing capabilities of the two institutions for advances in understanding key scientific problems of mutual interest and opening up broader educational opportunities for students and postdoctoral candidates (postdocs). Northwestern undergraduate students, graduate students and postdocs will be able to perform cutting edge science and technology research in accelerator and detector science and the physics of superconductivity at Fermilab and Northwestern under the joint direction of Fermilab researchers and Northwestern professors. Research program covers three thrusts below, with subtopics detailed in the CRADA: • Vortex dynamics in superconductors • Superconducting devices • New frontiers in microwave instrumentation/techniques.

47 OTHER INSTRUMENTATION↗
DOE OSTI2023

Ab Initio Transport Calculations: From Normal to Superconducting Current

Applying the Bogoliubov-de Gennes equations with density-functional theory, it is possible to formulate first principles description of current-phase relationships in superconducting/normal (magnetic)/superconducting tri-layers. Such structures are the basis for the superconducting analog of Magnetoresistive random access memory devices (JMRAM). In a recent paper1 we presented results from the first attempt to formulate such a theory, applied to the Nb/Ni/Nb trilayers. In the present work we provide computational details, explaining how to construct key ingredient (scattering matrices SN ) in a framework of linear muffin-tin orbitals (LMTO).

CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS↗
DOE OSTI2024

Multidimensional coherent spectroscopy of light-driven states and their collective modes in multiband superconductors

We present a comprehensive theory of light-controlled multiband superconductivity, and apply it to predict distinctive signatures of light-driven superconducting (SC) states in terahertz multidimensional coherent spectroscopy (THz-MDCS) experiments. We first derive gauge-invariant Maxwell-Bloch equations for multiband BCS superconductors with spatial fluctuations. We consider driving electromagnetic fields determined self-consistently by Maxwell's equations. By calculating the THz-MDCS spectra measured experimentally in the clean SC limit, we identify unique signatures of finite-momentum Cooper-pairing states that live longer than the laser pulse. They are controlled by a pair of THz laser pulses with well-defined relative phase (pulse pair). The pseudospin oscillators that describe the properties of these SC states are parametrically driven by both finite-momentum Cooper pairing and by time oscillations of the order-parameter relative phase. We show that such strong parametric driving leads to drastic changes in the THz-MDCS spectral shape from the predictions of third-order nonlinear susceptibility calculations. These spectral changes strongly depend on the interband-to-intraband interaction ratio and on the collective modes of the light-driven state. For negligible interband interaction, the spectra show a transition with increasing field, from traditional pump-probe, four-wave-mixing, and third-harmonic generation peaks determined by the laser frequency to sidebands determined by the excitations of the driven system. These sidebands emerge from difference-frequency Raman processes in the nonequilibrium SC state. For interband couplings weaker than the intraband pairing, we show that the Leggett phase collective mode leads to harmonic sidebands around the traditional pump-probe peaks. Additional Higgs collective mode peaks result from light-induced inversion-symmetry breaking in a thin-film geometry. For strong interband coupling, we find a transition from a nonequilibrium finite Cooper-pair momentum state characterized by hybrid-Higgs amplitude mode peaks in THz-MDCS spectra to a driven state identified experimentally by the emergence of Floquet-type sidebands at bi-Higgs frequencies. Those dominant bi-Higgs-frequency satellites are manifestations of a new order parameter relative phase collective mode that characterizes the nonequilibrium SC state. The predicted interaction- and field-dependent transitions in the spectral profile allow us to propose THz-MDCS experiments for quantum tomography of light-driven superconductivity.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Phase diagram of a bilayer superconductor under an in-plane magnetic field

We study a double layer superconductor in the presence of a parallel magnetic field Bby obtaining self-consistent solutions of the Bogoliubov-de Gennes equations, and also using the Pakrovsky- Talapov model for the free energy expressed in terms of the relative phase, namely the difference in the phases of the superconducting order parameters in the two layers. We find that with increasing B, a continuous transition occurs from the Bardeen-Cooper-Schrieffer (BCS) state, where the relative phase is constant, into a state which contains stripes of the BCS state separated by localized vortices in the relative phase. This state is predicted to manifest through oscillations in the amplitude of the superconducting gap and an alternating pattern of supercurrents. With increasing B, the BCS stripe state continuously evolves into the Fulde-Ferrell-Larkin-Ovchinnikov state with linearly varying relative phase and a constant gap amplitude. Furthermore, these predictions apply to superconductivity in bilayer transition-metal-dichalcogenide systems with Ising spin-orbit coupling, and ought to be testable in a recently studied experimental system.

2-dimensional systems↗
DOE OSTI2023

Roadmap on artificial intelligence and big data techniques for superconductivity

This paper presents a roadmap to the application of AI techniques and big data (BD) for different modelling, design, monitoring, manufacturing and operation purposes of different superconducting applications. To help superconductivity researchers, engineers, and manufacturers understand the viability of using AI and BD techniques as future solutions for challenges in superconductivity, a series of short articles are presented to outline some of the potential applications and solutions. These potential futuristic routes and their materials/technologies are considered for a 10–20 yr time-frame.

machine learning, neural network↗
DOE OSTI2026

Effect of non-stoichiometry and pressure on superconductivity in topological semimetal PdTe

Research into topological superconductivity has been at the forefront of condensed matter physics due to both fundamental interest and potential applications in quantum computing. PdTe, is such a superconductor with a transition temperature T c ∼ 4.5 K and exhibits a nontrivial topological electronic structure, thus receiving significant attention. We report an experimental and theoretical investigation of the pressure effect on superconductivity by applying chemical non-stoichiometry and hydrostatic pressure. While T c decreases with increasing pressure through electrical resistivity, magnetization, and specific heat measurements, chemical pressure has a distinct impact from hydrostatic pressure, which could increase T c by creating negative pressure via non-stoichiometric Pd x Te with x > 1. Accompanied with this is a sign change of the Hall coefficient from negative at x < 1 to positive at x > 1. This indicates extreme sensitivity of the electronic structure to chemical non-stoichiometry, which occurs as a Pd vacancy for x < 1 and Pd interstitial for x > 1.

nonstoichiometry↗
DOE OSTI2024

Growth of Native Oxides of Niobium Thin Films for Superconducting Qubits with Etching Chemistry

Niobium thin films have been broadly applied in building superconducting qubits for quantum computing hardware. While improvements have been made by device engineering efforts, scaling the energy-sensitive quantum system requires materials study for further improvements. In this study, we performed XPS and ToF-SIMS analysis for Nb thin films across samples with different manufacturing techniques. By varying the air exposure time of the samples, this research comparatively investigates the chemical and depth profile of native oxides before and after the etching process. We observe a rapid logarithmic growth of oxide thickness across all samples and the dominant presence and growth of Niobium pentoxide in atomic percentage concentration on the surface. This comparative study provides insight into oxides mitigation strategies and correlation with qubits performance.

Lei, Zhicheng↗
DOE OSTI2023

Electropolishing parameters study for surface smoothening of low-$\beta$650 MHz five-cell niobium superconducting radio frequency cavity

Electropolishing (EP) is applied to niobium (Nb) superconducting radio frequency (SRF) cavities, which are used in particle accelerators for their surface treatment. The EP process for 1.3 GHz cavities has been extensively studied earlier. In this work, a parametric study on EP of low-β (0.61) 650 MHz Nb SRF cavities (LB650), which will be used in pre-production cryomodule for proton improvement plan-II (PIP-II) linear accelerator, was conducted to determine adequate EP conditions for attaining a smooth surface of the cavities. EP performed with the standard parameters and an initial cathode (cathode-I) having a cathode surface area of ~5% of the cavity surface area yielded a rough equator surface of the cavity. The grain step height on the equator weld position was measured to be ~ 32 μm. The rough surface was attributed to preferential grain etching confirmed by a polarization curve showing a linear relationship between the EP current and voltage and the absence of the current plateau region. The cathode was modified to make its surface area twice that of cathode-I. The modified cathode (cathode-M) provided a current plateau region in the corresponding I-V curves measured at different cavity temperatures. The onset voltage for the plateau was found to be higher at higher cavity temperatures. Here this study revealed that even with cathode-M, the standard 18 V was low for EP of such large-sized cavities when the cavity temperature was 18 °C. EP performed at a higher voltage of 22–24.5 V with cathode-M yielded a smooth surface with a grain step height of only 0.6 μm. The applied EP conditions also improved removal uniformity along the cavity length. In contrast to the cavity treated with cathode-I, the cavities treated with cathode-M achieved a significantly higher accelerating gradient (E acc ) in vertical tests conducted in a cryostat at 2 K. The modified EP was found efficient to produce the cavities that achieved E acc of 22.4 MV/m, required by PIP II project in the baseline RF tests, to qualify for further surface processing used to enhance their quality factors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
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↗
DOE OSTI2023

Strain-switchable field-induced superconductivity

Field-induced superconductivity is a rare phenomenon where an applied magnetic field enhances or induces superconductivity. Here, we use applied stress as a control switch between a field-tunable superconducting state and a robust non–field-tunable state. This marks the first demonstration of a strain-tunable superconducting spin valve with infinite magnetoresistance. We combine tunable uniaxial stress and applied magnetic field on the ferromagnetic superconductor Eu(Fe 0.88 Co 0.12 ) 2 As 2 to shift the field-induced zero-resistance temperature between 4 K and a record-high value of 10 K. We use x-ray diffraction and spectroscopy measurements under stress and field to reveal that strain tuning of the nematic order and field tuning of the ferromagnetism act as independent control parameters of the superconductivity. Combining comprehensive measurements with DFT calculations, we propose that field-induced superconductivity arises from a novel mechanism, namely, the uniquely dominant effect of the Eu dipolar field when the exchange field splitting is nearly zero.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

INVESTIGATION OF THE MULTILAYER SHIELDING EFFECT THROUGH NbTiN-AlN COATED BULK NIOBIUM

Superconducting radio frequency (SRF) cavities, composed of bulk niobium (Nb), are extensively utilized in particle accelerators. To optimize their performance and extend their operational range, thin films of superconducting materials are applied to the Nb surfaces. This study focuses on investigating the magnetic field penetration characteristics of NbTiN-AlN coating on bulk niobium. The experimental setup involves measuring the magnetic field penetration across flat superconducting samples at cryogenic temperatures. One key parameter of interest is the field just before the first flux penetration, Bp which enables the observation of the multilayer shielding effect on bulk niobium under high magnetic fields. The study reveals a significant enhancement in Bp of the NbTiN-AlN coated Nb samples compared to bare Nb samples. This property holds critical importance for achieving high field performance in SRF cavities. Furthermore, the study explores the relationship between coating thickness and Bp corroborating the theoretical predictions.

Senevirathne, I. H.↗
DOE OSTI2024

Scanning SQUID study of ferromagnetism and superconductivity in infinite-layer nickelates

Infinite-layer nickelates R 1-x Sr x NiO 2 (R = La, Pr, Nd) are a class of superconductors with structural similarities to cuprates. Although long-range antiferromagnetic order has not been observed for these materials, magnetic effects such as antiferromagnetic spin fluctuations and spin-glass behavior have been reported. Different experiments have drawn different conclusions about whether the pairing symmetry is s or d wave. In this paper, we applied a scanning superconducting quantum interference device (SQUID) to probe the magnetic behavior of film samples of three infinite-layer nickelates (La 0.85 Sr 0.15 NiO 2 , Pr 0.8 Sr 0.2 NiO 2 , and Nd 0.775 Sr 0.225 NiO 2 ) grown on SrTiO 3 (STO), each with a nominal thickness of 20 unit cells. In all three films, we observed a ferromagnetic background. We also measured the magnetic susceptibility above the superconducting critical temperature in Pr 0.8 Sr 0.2 NiO 2 and La 0.85 Sr 0.15 NiO 2 and identified a non-Curie-Weiss dynamic susceptibility. Both magnetic features are likely due to NiO x nanoparticles. We investigated superconductivity in Pr 0.8 Sr 0.2 NiO 2 and Nd 0.775 Sr 0.225 NiO 2 , which exhibited inhomogeneous diamagnetic screening. The superfluid density inferred from the diamagnetic susceptibility in relatively homogeneous regions shows T-linear behavior in both samples. Finally, we observed superconducting vortices in Nd 0.775 Sr 0.225 NiO 2 . We determined a Pearl length of 330 µm for Nd 0.775 Sr 0.225 NiO 2 at 300 mK, both from the strength of the diamagnetism and from the size and shape of the vortices. These results highlight the importance of considering NiO x particles when interpreting experimental results for these films.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗