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All sources NASA NTRS DOE OSTI

DOE OSTI2025

QSHS: an axion dark matter resonant search apparatus

We describe a resonant cavity search apparatus for axion dark matter constructed by the quantum sensors for the hidden sector collaboration. The apparatus is configured to search for QCD axion dark matter, though also has the capability to detect axion-like particles, dark photons, and some other forms of wave-like dark matter. Initially, a tuneable cylindrical oxygen-free copper cavity is read out using a low noise microwave amplifier feeding a heterodyne receiver. The cavity is housed in a dilution refrigerator (DF) and threaded by a solenoidal magnetic field, nominally 8 T. The apparatus also houses a magnetic field shield for housing superconducting electronics, and several other fixed-frequency resonators for use in testing and commissioning various prototype quantum electronic devices sensitive at a range of axion masses in the range 2.0–40 μ eV c -2 . The apparatus as currently configured is intended as a test stand for electronics over the relatively wide frequency band attainable with TM 010 the cavity mode used for axion searches. We present performance data for the resonator, DF, and magnet, and plans for the first science run.

Physics - Physics of elementary particles and fiel↗

DOE OSTI2022

Design of the Fermilab Pre-Series Cold Mass for the HL-LHC Accelerator Upgrade Project

Here as part of the U.S. contribution to the HL-LHC Accelerator Upgrade Project (AUP), Fermilab is designing and building cold masses suitable for use in the LHC interaction regions. The cold mass provides a vacuum-tight helium enclosure for the magnets. Two magnets are aligned both axially and in cross section at Fermilab based on survey and warm magnetic measurements. Bus work and instrumentation is added. A welded stainless steel vacuum-tight shell surrounds the two magnets, and the structure is prepared for insertion into the cryostat. This paper summarizes the design of the cold mass including alignment, bus work, weld details, and instrumentation.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2023

AUP first Pre-series Cold Mass Installation into the Cryostat

For the Hi-Lumi LHC Upgrade (HL-LHC) new high field and large-aperture quadrupole magnets for the low-beta inner triplets (Q1, Q2, Q3) are being built. These new quadrupole magnets are based on Nb3Sn superconducting technology. As part of the US-HiLumi Accelerator Upgrade Project (AUP) ten Cryostat Assemblies (LQXFA) for Q1 and Q3 replacement will be built, tested and delivered to CERN. The first of the LQXFA was assembled and tested at Fermi National Accelerator Laboratory (FNAL) during the fall of 2022 and spring 2023. We will present the integration work of the Cold Mass assembly into the Cryostat Kit provided by CERN. Each Cold Mass contains two trained MQXFA magnets of ~ 5 m length installed in a stainless-steel helium pressure vessel. The Cold Mass will be surrounded by cryostat shields, piping, and vacuum vessel. We will discuss the metrology survey results and present the LQXFA measurements prior testing at the Fermilab Magnet Test facility and lessons learned.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS1991

Composite superconducting wires obtained by high-rate tinning in molten Bi-Pb-Sr-Ca-Cu-O system

Long lengths of metal superconductor composites were prepared by passing a copper wire through the bismuth based molten oxide system at a constant speed. The key to successful composite preparation is the high pulling speed involved, which permits minimization of the severe interaction between the unbuffered metal surface and the oxide melt. Depending on the temperature of the melt and the pulling speed, a coating with different thickness and microstructure appeared. The nonannealed thick coatings contained a Bi2(Sr,Ca)2Cu1O6 phase as a major component. After relatively short time annealing at 800 C, both resistivity and initial magnetization versus temperature measurements show superconducting transitions beginning in the 110 to 115 K region. The effects of annealing and composition on obtained results are discussed. This method of manufacture led to the fabrication of wire with a copper core in a dense covering with uniform thickness of about h approximately equal to 5 to 50 microns. Composite wires with h approximately equal to 10 microns (h/d approximately equal to 0.1) sustained bending on a 15 mm radius frame without cracking during flexing.

Grosav, A. D.↗

DOE OSTI2024

Designing phase sensitive probes of monopole superconducting order

Distinct from familiar s-, p-, or d-wave pairings, the monopole superconducting order represents a novel class of pairing order arising from nontrivial monopole charge of the Cooper pair. In the weak-coupling regime, this order can emerge when pairing occurs between Fermi surfaces with different Chern numbers in, for example, doped Weyl semimetal systems. However, the phase of monopole pairing order is not well-defined over an entire Fermi surface, making it challenging to design experiments sensitive to both its symmetry and topology. To address this, we propose a scheme based on symmetry and topological principles to identify this elusive pairing order through a set of phase-sensitive Josephson experiments. By examining the discrepancy between global and local angular momentum of the pairing order, we can unveil the monopole charge of the pairing order, including for models with higher pair monopole charge |q p |=1,2, and 3. We demonstrate the proposed probe of monopole pairing order through analytic and numerical studies of Josephson coupling in models of monopole superconductor junctions. This work opens a promising avenue to uncover the unique topological properties of monopole pairing orders and to distinguish them from known pairing orders based on spherical harmonic symmetry.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS1973

Initial results from the NASA Lewis Bumpy Torus experiment

Initial results were obtained from low power operation of the NASA Lewis Bumpy Torus experiment, in which a steady-state ion heating method based on the modified Penning discharge is applied in a bumpy torus confinement geometry. The magnet facility consists of 12 superconducting coils, each 19 cm i.d. and capable of 3.0 T, equally spaced in a toroidal array 1.52 m in major diameter. A 18 cm i.d. anode ring is located at each of the 12 midplanes and is maintained at high positive potentials by a dc power supply. Initial observations indicate electron temperatures from 10 to 150 eV, and ion kinetic temperatures from 200 eV to 1200 eV. Two modes of operation were observed, which depend on background pressure, and have different radial density profiles. Steady state neutron production was observed. The ion heating process in the bumpy torus appears to parallel closely the mechanism observed when the modified Penning discharge was operated in a simple magnetic mirror field.

Roth, J. R.↗

DOE OSTI2020

Crystal orientation dependence of interfacial magnetic anisotropy at heavy-metal/magnetic-garnet interfaces

Ferrimagnetic insulators capped with a heavy metal are becoming an increasingly interesting materials system in spintronics due to their unique ability for electrical manipulation and detection of magnetic states and spin textures via spin-orbit torques. The ability to engineer magnetic anisotropy is a powerful tool for tuning the recently discovered phenomena in these bilayers such as electrical switching or the stabilization of topological magnetic textures. Here, we observe large shifts in the magnetic anisotropy in Tm 3 Fe 5 O 13 and Y 3 Fe 5 O 12 thin films due to heavy-metal capping layers, which strongly depends on the orientation of the substrate and therefore the orientation of the epitaxial films. This work suggests large Rashba spin-orbit coupling at the metal/ferrimagneticinsulator interface, which can be engineered in spintronic devices that utilize spin-orbit torques for electrical control of the magnetization in magnetic insulators.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2021

Coupled electronic and magnetic relaxation in Fe 1+y Te: direct evidence for the interaction between itinerant carriers and local moments

Iron chalcogenides are of particular interests among iron-based superconductors due to their distinct properties such as high-T c on FeSe monolayer and competing magnetic correlations in Fe 1+y Te. Here, in this work, we report unusual transport properties observed near the critical composition of Fe 1+y Te (y ~ 0.09) where competing magnetic correlations exist. The resistivity exhibits surprising temperature-dependent relaxation behavior below T N , resulting in the increase of resistivity with time for 35 K < T < T N , but the decrease of resistivity with time for 10 K < T < 35 K. Such resistivity relaxation is intimately coupled to the magnetization relaxation and can be attributed to the glassy magnetic states induced by the competing magnetic orders. These findings demonstrate strong coupling between itinerant carriers and local ordered moments in Fe 1+y Te.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2021

In-Plane Critical Magnetic Fields in Magic-Angle Twisted Trilayer Graphene

It has recently been shown that superconductivity in magic-angle twisted trilayer graphene survives to in-plane magnetic fields that are well in excess of the Pauli limit, and much stronger than the in-plane critical magnetic fields of magic-angle twisted bilayer graphene. The difference is surprising because twisted bilayers and trilayers both support the magic-angle flat bands thought to be the fountainhead of twisted graphene superconductivity. In this study, we show that the difference in critical magnetic fields can be traced to a C 2 M h symmetry in trilayers that survives in-plane magnetic fields, and also relative displacements between top and bottom layers that are not under experimental control at present. An gate electric field breaks the C 2 M h symmetry and therefore limits the in-plane critical magnetic field.

2-dimensional systems↗

DOE OSTI2022

Magnetic field screening in hydrogen-rich high-temperature superconductors

In the last few years, the superconducting transition temperature, T c , of hydrogen-rich compounds has increased dramatically, and is now approaching room temperature. However, the pressures at which these materials are stable exceed one million atmospheres and limit the number of available experimental studies. Superconductivity in hydrides has been primarily explored by electrical transport measurements, whereas magnetic properties, one of the most important characteristic of a superconductor, have not been satisfactory defined. Here, we develop SQUID magnetometry under extreme high-pressure conditions and report characteristic superconducting parameters for Im-3m-H 3 S and Fm-3m-LaH 10 —the representative members of two families of high-temperature superconducting hydrides. We determine a lower critical field H c1 of ~0.82 T and ~0.55 T, and a London penetration depth λ L of ~20 nm and ~30 nm in H 3 S and LaH 10 , respectively. The small values of λ L indicate a high superfluid density in both hydrides. These compounds have the values of the Ginzburg-Landau parameter κ ~12–20 and belong to the group of “moderate” type II superconductors, rather than being hard superconductors as would be intuitively expected from their high T c s.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2020

Quasiclassical Theory of C4-Symmetric Magnetic Order in Disordered Multiband Metals

Recent experimental studies performed in the normal state of iron-based superconductors have discovered the existence of the C 4 -symmetric (tetragonal) itinerant magnetic state. This state can be described as a spin density wave with two distinct magnetic vectors Q → 1 and Q → 2 . Given an itinerant nature of magnetism in iron-pnictides, we develop a quasiclassical theory of tetragonal magnetic order in disordered three-band metal with anisotropic band structure. Within our model we find that the C 4 -symmetric magnetism competes with the C 2 -symmetric state with a single Q → magnetic structure vector. Our main results is that disorder promotes tetragonal magnetic state which is in agreement with earlier theoretical studies.

74.45.c, 74.50. r, 74.20.R↗

DOE OSTI2021

Direct evidence of microstructure dependence of magnetic flux trapping in niobium

Abstract Elemental type-II superconducting niobium is the material of choice for superconducting radiofrequency cavities used in modern particle accelerators, light sources, detectors, sensors, and quantum computing architecture. An essential challenge to increasing energy efficiency in rf applications is the power dissipation due to residual magnetic field that is trapped during the cool down process due to incomplete magnetic field expulsion. New SRF cavity processing recipes that use surface doping techniques have significantly increased their cryogenic efficiency. However, the performance of SRF Nb accelerators still shows vulnerability to a trapped magnetic field. In this manuscript, we report the observation of a direct link between flux trapping and incomplete flux expulsion with spatial variations in microstructure within the niobium. Fine-grain recrystallized microstructure with an average grain size of 10–50 µm leads to flux trapping even with a lack of dislocation structures in grain interiors. Larger grain sizes beyond 100–400 µm do not lead to preferential flux trapping, as observed directly by magneto-optical imaging. While local magnetic flux variations imaged by magneto-optics provide clarity on a microstructure level, bulk variations are also indicated by variations in pinning force curves with sequential heat treatment studies. The key results indicate that complete control of the niobium microstructure will help produce higher performance superconducting resonators with reduced rf losses 1 related to the magnetic flux trapping.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2023

Linear magnetic susceptibility of anisotropic superconductors of cuboidal shape

In this study, a simplified model of anisotropic magnetic susceptibility in the Meissner–London vortex-free state of cuboidal superconducting samples is presented. Using this model, precision measurements of the magnetic response in three perpendicular directions of a magnetic field with respect to primary crystal axes can be used to extract the components of the London penetration depth, thus enabling the evaluation of the general superfluid density tensor, which is needed in the analysis of the superconducting gap structure.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2020

22 K superconductivity in Ba Fe 2 As 2 exposed to F 2

Several previous reports on undoped AEFe 2 As 2 (AE = alkaline earth metal) point to drops in resistivity indicative of possible superconductivity and some degree of Meissner effect in the magnetic susceptibility. Also, based on both resistivity and magnetic susceptibility measurements, controlled exposure to water vapor has been shown to induce superconductivity in AEFe 2 As 2 . In our study, BaFe 2 As 2 single crystals grown using the self-flux method showed a full resistive drop around 22 K and magnetic shielding, when exposed to fluorine gas postgrowth. Our measurements indicate electron (donor) doping via atomic substitution of F for As is concurrent with the observed superconductivity, which sheds light on the likely effect of exposure to water vapor in previous work. Like doping experiments (such as substitution of Co for Fe, P for As, or K for Ba) in AEFe 2 As 2 to date, the present work is consistent with suppression of the spin density wave transition coincident with the appearance of T c . In addition to answering the puzzle of superconductivity in undoped or water vapor exposed AEF 2 As 2 , our results also represent a fast (20 min exposure to 5% F in He) and reliable method suitable for inducing superconductivity in thin films of AEFe 2 As 2 . As a result, some supportive work on BaFe 2 As 2 exposed to Cl 2 is also presented.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Tuning superconductivity and spin-vortex instabilities in CaKFe 4 As 4 through in-plane antisymmetric strains

Lattice strains of appropriate symmetry have served as an excellent tool to explore the interaction of superconductivity in the iron-based superconductors with orthorhombic-nematic and stripe spin-density-wave (SSDW) order. In this Letter, we contribute to a broader understanding of the coupling of strain to superconductivity and competing normal-state orders by studying CaKFe 4 As 4 under large, in-plane strains of B 1 g and B 2 g symmetry. In contrast to the majority of iron-based superconductors, pure CaKFe 4 As 4 exhibits superconductivity with a relatively high transition temperature of T c ∼ 35 K in proximity of a noncollinear, tetragonal, hedgehog spin-vortex crystal (SVC) order. Through experiments and calculations, we demonstrate an anisotropic in-plane strain response of T c and the favored SVC configuration in CaKFe 4 As 4 . This supports a scenario, in which the change in spin fluctuations dominates the strain response of superconducting T c . Overall, by suggesting moderate B 2 g strains as an effective parameter to change the stability of SVC and SSDW, we outline a pathway to a unified phase diagram of iron-based superconductivity. Published by the American Physical Society 2024

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS1995

Thallium 2223 high T(sub c) superconductor in a silver matrix and its magnetic shielding, hermalcycle and time aging properties

Superconducting Tl2Ba2Ca2Cu3O10 (Tl2223) was ground to powder. Mixture with silver powder (0-80% weight) and press to desired shape. After proper annealing, one can get good silver-content Tl2223 bulk superconductor. It is time-stable and has good superconducting property as same as pure Tl2223. It also has better mechanical property and far better thermal cycle property than pure Tl2223.

Fei, X.↗

DOE OSTI2023

Stabilization of collinear ferromagnetic order in Ir-doped triple-layer ruthenate Sr 4 Ru 3 O 10

The triple-layer Sr 4 Ru 3 O 10 is a spin-orbit-coupled metal featuring an intriguing combination of ferromagnetic and metamagnetic states. Here we report a comprehensive study of single-crystal neutron and x-ray diffraction on Sr 4 Ru 3 O 10 with 4% iridium doping. The system crystallizes in an orthorhombic Bbem structure in which two triple layers are related by a base centering symmetry operation within one unit cell. The 4% Ir doping at the Ru site sensitively alters the structural balance between the RuO 6 layers, as such the two outer-layer octahedra rotate 6.7° about the c axis, while the central-layer one rotates in the opposite direction by 11.0°. The increased lattice distortion stabilizes a collinear ferromagnetic state with magnetic moments fully aligned along the c axis. The emerging perpendicular magnetic anisotropy naturally increases the critical field for the inplane metamagnetic transition to 4.5 Tesla. All results highlight the critical linkage between the magnetic properties and underlying lattice through orbital degrees of freedom, as well as the enhanced spin orbit coupling due to heavier 5d ions. Our observation provides a viable route for an efficient manipulation of the magnetic states with functionalities.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2022

Quantum Computing with Majorana Kramers Pairs

Here, we propose a universal gate set acting on a qubit formed by the degenerate ground states of a Coulomb-blockaded time-reversal invariant topological superconductor island with spatially separated Majorana Kramers pairs: the “Majorana Kramers qubit.” All gate operations are implemented by coupling the Majorana Kramers pairs to conventional superconducting leads. Interestingly, in such an all-superconducting device, the energy gap of the leads provides another layer of protection from quasiparticle poisoning independent of the island charging energy. Moreover, the absence of strong magnetic fields—which typically reduce the superconducting gap size of the island—suggests a unique robustness of our qubit to quasiparticle poisoning due to thermal excitations. Consequently, the Majorana Kramers qubit should benefit from prolonged coherence times and may provide an alternative route to a Majorana-based quantum computer.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗