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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Low Temperature and Surfactant-Free Hydrothermal Synthesis of CoNi Nanoparticles: Structure, Microstructure, and Magnetic Properties

We report on the synthesis of Co{sub 30}Ni{sub 70} nanoparticles using hydrothermal method at low temperatures and short times (100 °C, 2 h) without any surfactant or external magnetic field. The effect of NaOH concentration on the crystal structure, microstructure, and magnetic properties of CoNi samples has been investigated by x-ray diffraction (XRD), scanning (SEM) and high-resolution transmission (HRTEM) electron microscopy, and vibrating sample magnetometry (VSM). From the Rietveld refinement of x-ray powder diffraction patterns, we have evidenced the coexistence of two phases with face-centered cubic (FCC) and hexagonal (HCP) crystal structures, being 12 nm and 3 nm, respectively, the values for the mean grain size of both phases. SEM images show that the basic microstructure is composed of quasi-spheres and a chain-like morphology appears with increasing the amount of NaOH. HRTEM images evidence the formation of such chains, and confirm the coexistence of FCC and HCP phases. The magnetic hysteresis loops show a clear dependence of the coercivity on the particle morphology indicating the role played by the magnetic shape anisotropy.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2012

Nanocrystalline sol-gel TiO{sub 2}-SnO{sub 2} coatings: Preparation, characterization and photo-catalytic performance

Highlights: Black-Right-Pointing-Pointer SnO{sub 2} additive enhanced significantly photo-catalytic properties of TiO{sub 2} based thin film for remove of organic compounds. Black-Right-Pointing-Pointer Structural and optical properties are dependent on dopant concentration. Black-Right-Pointing-Pointer TiO{sub 2}-SnO{sub 2} nanocrystalline thin film is promising for photocatalytic properties in visible light. -- Abstract: In this study, preparation of SnO{sub 2} (0-30 mol% SnO{sub 2})-TiO{sub 2} dip-coated thin films on glazed porcelain substrates via sol-gel process has been investigated. The effects of SnO{sub 2} on the structural, optical, and photo-catalytic properties of applied thin films have been studied by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Surface topography and surface chemical state of thin films were examined by atomic force microscopy and X-ray photoelectron spectroscopy. XRD patterns showed an increase in peak intensities of the rutile crystalline phase by increasing the SnO{sub 2} content. The prepared Sn doped TiO{sub 2} photo-catalyst films showed optical absorption in the visible light area exhibited excellent photo-catalytic ability for the degradation of methylene blue under visible light irradiation. Best photo-catalytic activity of Sn doped TiO{sub 2} thin films was measured in the TiO{sub 2}-15 mol% SnO{sub 2} sample by the Sn{sup 4+} dopants presented substitution Ti{sup 4+} into the lattice of TiO{sub 2} increasing the surface oxygen vacancies and the surface hydroxyl groups.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Morphogenesis of spin cycloids in a noncollinear antiferromagnet

Pattern formation in spin systems with continuous-rotational symmetry (CRS) provides a powerful platform to study emergent complex magnetic phases and topological defects in condensed-matter physics. However, its understanding and correlation with unconventional magnetic order along with high-resolution nanoscale imaging are challenging. Here, we employ scanning nitrogen vacancy (NV) magnetometry to unveil the morphogenesis of spin cycloids at both the local and global scales within a single ferroelectric domain of (111)-oriented BiFeO 3 , which is a noncollinear antiferromagnet, resulting in formation of a glassy labyrinthine pattern. We find that the domains of locally oriented cycloids are interconnected by an array of topological defects and exhibit isotropic energy landscape predicted by first-principles calculations. We propose that the CRS of spin-cycloid propagation directions within the (111) drives the formation of the labyrinthine pattern and the associated topological defects such as antiferromagnetic skyrmions. Unexpectedly, reversing the as-grown ferroelectric polarization from [$\overline{1}$ $\overline{1}$ $\overline{1}$] to [111] produces a noncycloidal NV image contrast which ¯ could be attributed to either the emergence of a uniformly magnetized state or a reversal of the cycloid polarity. These findings highlight that (111)-oriented BiFeO 3 is not only important for studying the fascinating subject of pattern formation but could also be utilized as an ideal platform for integrating novel topological defects in the field of antiferromagnetic spintronics.

magnetoelectric↗
DOE OSTI2012

Steam-assisted crystallization of TPA{sup +}-exchanged MCM-41 type mesoporous materials with thick pore walls

Highlights: ► Mesoporous Ti-containing silica with thicker pore walls was synthesized. ► Ion-exchange and steam-assisted crystallization led to MCM-41/MFI composite. ► The introduction of Ti inhibited the formation of separated MFI particles. ► Lower temperature favored retaining mesoporous characteristics and morphology. -- Abstract: Hierarchical MCM-41/MFI composites were synthesized through ion-exchange of as-made MCM-41 type mesoporous materials with tetrapropylammonium bromide and subsequent steam-assisted recrystallization. The obtained samples were characterized by powder X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis, FT-IR, {sup 1}H–{sup 13}C CP/MAS and nitrogen adsorption–desorption. The XRD patterns show that the MCM-41/MFI composite possesses both ordered MCM-41 phase and zeolite MFI phase. SEM and TEM images indicate that the recrystallized materials retained the mesoporous characteristics and the morphology of as-made mesoporous materials without the formation of bulky zeolite, quite different from the mechanical mixture of MCM-41 and MFI structured zeolite. Among others, lower recrystallization temperature and the introduction of the titanium to the parent materials are beneficial to preserve the mesoporous structure during the recrystallization process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Microstructural strain mapping during in-situ cyclic testing of ductile iron

Highlights: • A method for quantitative study of crack formation and propagation during cyclic loading was developed. • Focused Ion Beam Milling was shown to be an effective method to generate a high quality speckle pattern for Digital Image Correlation measurements • The method enabled a high-resolution measurement of localized strain in the microstructure of ductile iron • The peak strain and the strain distribution ahead of the growing crack under load were quantified - Abstract: This paper focuses on local strain distribution in the microstructure of high silicon ductile iron during cyclic loading. In-situ cyclic test was performed on compact-tension (CT) samples inside the scanning electron microscope (SEM) to record the whole deformation and obtain micrographs for microstructural strain measurement by means of digital image correlation (DIC) technique. Focused ion beam (FIB) milling was used to generate speckle patterns necessary for DIC measurement. The equivalent Von Mises strain distribution was measured in the microstructure at the maximum applied load. The results revealed a heterogeneous strain distribution at the microstructural level with higher strain gradients close to the notch of the CT sample and accumulated strain bands between graphite particles. Local strain ahead of the early initiated micro-cracks was quantitatively measured, showing high strain localization, which decreased by moving away from the micro-crack tip. It could be observed that the peak of strain in the field of view was not necessarily located ahead of the micro-cracks tip which could be because of the (i) strain relaxation due to the presence of other micro-cracks and/or (ii) presence of subsurface microstructural features such as graphite particles that influenced the strain concentration on the surface.

36 MATERIALS SCIENCE↗
DOE OSTI2026

A ModEx Framework for Watershed Subsurface Investigation With Limited Geophysical Data Using Machine Learning and Hydrologic Modeling

Abstract Subsurface heterogeneity influences watershed hydrology strongly but remains difficult to characterize at catchment scales with sparse and costly field data. Geophysical surveys such as electromagnetic induction (EMI) provide local spatial subsurface images yet scaling them to watershed scales and converting EMI‐derived resistivity into hydraulic properties remains a challenge. We present a Model–Experiment (ModEx) framework that integrates limited EMI data with machine learning (ML) and hydrologic modeling to improve process representation and guide field investigations. Sparse EMI surveys were scaled to the catchment scale using a Random Forest model, and the resulting resistivity fields were combined with nearby borehole constraints to parameterize a hydrologic model. The EMI‐informed hydrological simulations improved predictions of streamflow sustained by subsurface flow and shallow saturation patterns. By combining EMI data and ML with hydrologic modeling, the ModEx framework guides future subsurface surveys, providing a transferable and efficient strategy for data–model integration across diverse watersheds. Plain Language Summary Mapping the underground network of soil and rock that controls water is essential for predicting floods and droughts, but seeing underground is difficult and expensive. We cannot drill everywhere, so scientists use geophysical tools to scan broad areas. There are two key challenges: these geophysical scans are often sparse across the whole watershed, and the geophysical data is hard to translate into water‐related properties. We used artificial intelligence to solve these problems. We taught a computer to find patterns linking the limited geophysical data to the land surface properties. This allowed it to fill in the gaps and create a complete, useful subsurface map for the entire watershed. This new map improves hydrologic simulations, leading to more accurate predictions of water movement in the watershed. It also helps scientists build better models with less data and generates a priority map showing where to measure next, making future investigations more efficient. Key Points Limited EMI scaled with ML improves catchment‐scale subsurface parameterization for hydrologic models The framework integrates hydrologic modeling with limited geophysical data to support subsurface investigation design ModEx framework offers a transferable data–model integration strategy that quantifies and reduces uncertainty guiding watershed studies

Chen, Hang↗
DOE OSTI2014

Investigation of nanocrystalline zinc chromite obtained by two soft chemical routes

Graphical abstract: - Highlights: • Two soft chemical routes to synthesize zinc chromites are described. • Glycine is used as chelating agent (precursor method) and fuel (solution combustion method). • The synthesized chromites have crystallite size in the range of 18–27 nm. • An antiferromagnetic (AFM) transition is observed at about T{sub N} ∼ 18 K. - Abstract: Zinc chromite (ZnCr{sub 2}O{sub 4}) nanocrystalline powders were obtained by two different chemical routes: the precursor method and the solution combustion method involving glycine-nitrates. The complex compound precursors, [ZnCr{sub 2}(NH{sub 2}CH{sub 2}COO){sub 8}]·9H{sub 2}O and [ZnCr{sub 2}(NH{sub 2}CH{sub 2}COOH){sub 4.5}]·(NO{sub 3}){sub 8}·6H{sub 2}O, were characterized by chemical analysis, infrared spectroscopy (IR), ultraviolet–visible spectroscopy (UV–vis) and thermal analysis. The structure, morphology, surface chemistry and magnetic properties of ZnCr{sub 2}O{sub 4} powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), infrared and Raman spectroscopy (RS), ultraviolet–visible spectroscopy (UV–vis) and magnetic measurements. X-ray diffraction patterns indicated the chromite spinel phase with good crystallinity and an average crystallite size of approximately 18–27 nm. The band gap values ranged between 3.31 and 3.33 eV. The magnetic measurements indicated an antiferromagnetic transition at T{sub N} ∼ 17.5/18 K.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Cytotoxic and antioxidant activity of the biogenic bismuth nanoparticles produced by Delftia sp. SFG

Highlights: • A bismuth nanoparticle (Bi NPs) producer bacterium, Delftia sp. SFG, was screened. • The Bi NPs was purified by a three phase partitioning system and characterized. • Cytotoxicity and antioxidant activity of biogenic Bi NPs were determined. - Abstract: In the present investigation a bismuth nanoparticles (Bi NPs) producing bacterial strain (designated as Delftia sp. SFG) was isolated from salt marsh and the biogenic Bi NPs was purified, characterized, and their cytotoxic and antioxidant activities were determined. The spherical shaped Bi NPs was inspected by transmission electron microscopy (TEM), scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX) microanalyzer, and X-ray diffraction spectroscopy (XRD) method. Furthermore, the related size distribution pattern (20–120 nm), UV–vis and Fourier transform infrared (FTIR) spectrums of the produced Bi NPs were determined. The attained results of cytotoxic effect (determined by MTT-based colorimetric assay) of the purified Bi NPs revealed IC{sub 50} of 10.9 ± 0.9 μg mL{sup −1}, 35.4 ± 0.5 μg mL{sup −1}, and 42.8 ± 1.7 μg mL{sup −1} against A549, MCF-7, and 3T3 cell lines. Determination of antioxidant activity showed IC{sub 50} values of 123.1 μg mL{sup −1} and 307.2 μg mL{sup −1} for butylated hydroxyanisole (BHA) and Bi NPs, respectively.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2012

Thermal expansion of Ba{sub 2}ZnSi{sub 2}O{sub 7}, BaZnSiO{sub 4} and the solid solution series BaZn{sub 2-x}Mg{sub x}Si{sub 2}O{sub 7} (0{<=}x{<=}2) studied by high-temperature X-ray diffraction and dilatometry

The thermal expansion behavior of Ba{sub 2}ZnSi{sub 2}O{sub 7}, BaZnSiO{sub 4} and BaZn{sub 2}Si{sub 2}O{sub 7} is characterized by both high-temperature X-ray diffraction (HT-XRD) and dilatometry. Ba{sub 2}ZnSi{sub 2}O{sub 7} and BaZnSiO{sub 4} show a thermal expansion (100-800 Degree-Sign C) in the range from 8.9 to 10.4 Multiplication-Sign 10{sup -6} K{sup -1}. By contrast, BaZn{sub 2}Si{sub 2}O{sub 7} has a much higher thermal expansion in the low-temperature modification and shows a phase transition at 280 Degree-Sign C which runs parallel with a steep increase in cell volume. This phase transition is also observed in the solid solution series BaZn{sub 2-x}Mg{sub x}Si{sub 2}O{sub 7}, but it is shifted to higher temperatures and to a smaller volume change with increasing Mg{sup 2+} concentration. This solid solution series is characterized by dilatometry, X-ray diffraction and differential scanning calorimetry. An adjustment of the MgO/ZnO-ratio enables the preparation of materials with a large variety of thermal expansions. - Graphical abstract: XRD-patterns of Ba{sub 2}ZnSi{sub 2}O{sub 7} were recorded at different temperatures (left). For each XRD-pattern a Rietveld-refinement was performed, the image in the middle shows the XRD-pattern measured at room temperature (circles), the Rietveld calculation (red line) and the difference between them (blue line). The lattice parameters derived hereof were plottet against the temperature and fitted to a polynomial (right picture). From those polynomials the lattice expansion was calculated. Highlights: Black-Right-Pointing-Pointer We examined the thermal expansion of Ba{sub 2}ZnSi{sub 2}O{sub 7}, BaZnSiO{sub 4} and BaZn{sub 2-x}Mg{sub x}Si{sub 2}O{sub 7}. Black-Right-Pointing-Pointer Thermal expansions were determined by dilatometry and high-temperature X-ray diffraction. Black-Right-Pointing-Pointer High-temperature X-ray diffraction enabled to determine anisotropic thermal expansion. Black-Right-Pointing-Pointer BaZn{sub 2}Si{sub 2}O{sub 7} exhibits the highest thermal expansion due to a phase transition. Black-Right-Pointing-Pointer Substitution of small amounts of Zn{sup 2+} for Mg{sup 2+} leads to a decrease in thermal expansion.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Comparison of Dislocation Characterization by Electron Channeling Contrast Imaging and Cross-Correlation Electron Backscattered Diffraction

The characterization and quantification of dislocations is predominately carried out using transmission electron microscopy (TEM). Nevertheless, the sample preparation necessary for TEM foils can be cumbersome and possibly introduce defects. Two other techniques for characterizing and quantifying dislocations are electron channeling contrast imaging (ECCI) and cross-correlation electron backscattered diffraction (CC-EBSD). ECCI is similar to TEM in that specific imaging (channeling or diffraction) conditions need to be established, but is carried out in a scanning electron microscope on bulk samples, resulting in less complex sample preparation. CC-EBSD measures subtle changes in orientation measured from EBSD patterns to calculate elastic strains and the Nye tensor to deduce and map the total geometrically necessary dislocation (GND) content. Furthermore, this work presented here compares the capabilities of ECCI and CC-EBSD to map dislocations generated from nanoindentation.

42 ENGINEERING↗
DOE OSTI2015

Flexible and High Performance Supercapacitors Based on NiCo2O4for Wide Temperature Range Applications

Binder free nanostructured NiCo 2 O 4 were grown using a facile hydrothermal technique. X-ray diffraction patterns confirmed the phase purity of NiCo 2 O 4 . The surface morphology and microstructure of the NiCo 2 O 4 analyzed by scanning electron microscopy (SEM) showed flower-like morphology composed of needle-like structures. The potential application of binder free NiCo 2 O 4 as an electrode for supercapacitor devices was investigated using electrochemical methods. The cyclic voltammograms of NiCo2O4 electrode using alkaline aqueous electrolytes showed the presence of redox peaks suggesting pseudocapacitance behavior. Quasi-solid state supercapacitor device fabricated by sandwiching two NiCo 2 O 4 electrodes and separating them by ion transporting layer. The performance of the device was tested using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The device showed excellent flexibility and cyclic stability. The temperature dependent charge storage capacity was measured for their variable temperature applications. Specific capacitance of the device was enhanced by ~150% on raising the temperature from 20 to 60°C. Hence, the results suggest that NiCo 2 O 4 grown under these conditions could be a suitable material for high performance supercapacitor devices that can be operated at variable temperatures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Electroplated L1{sub 0} CoPt thick-film permanent magnets

The fabrication and magnetic characterization of 15-μm-thick electroplated L1{sub 0} CoPt hard magnets with good magnetic properties is reported in this paper. Experimental study of the dependence of the magnets' properties on annealing temperature reveals that an intrinsic coercivity H{sub ci} = ∼800 kA/m (10 kOe), squareness >0.8, and energy product of >150 kJ/m{sup 3} are obtained for photolithographically patterned structures (250 μm × 2 mm stripes; 15 μm thickness) electroplated on silicon substrates and annealed in hydrogen forming gas at 700 °C. Scanning electron microscopy is used to inspect the morphology of both the as-deposited and annealed magnetic layers, and X-ray Diffractometer analysis on the magnets annealed at 700 °C confirm a phase transformation to an ordered L1{sub 0} CoPt structure, with a minor phase of hcp Co. These thick films are intended for microsystems/MEMS applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Low temperature dielectric and conductivity relaxation studies on magnetoelectric Pb(Fe{sub 2/3}W{sub 1/3})O{sub 3}

The single phase perovskite Pb(Fe{sub 2/3}W{sub 1/3})O{sub 3} [PFW] was synthesized by modified low – temperature (sintering at 850°C) solid-state reaction. Rietveld refinement ofroom temperature (RT) X-ray diffraction (XRD) and neutron diffraction (ND) patterns of the samples confirm the single phase formation with cubic structure (Pm-3m). Surface morphology of the compounds was studied by Scanning electron microscope (SEM) and average grain size was estimated to be ∼2 µm. The RT dielectric properties of PFW ceramic are studied as a function of frequency from 100 - 1MHz. The temperature dependent (120 – 293K) dielectric properties were studied at few selected frequencies. We found the frequency dependent dielectric constant shows increasing trend with increase in temperature from 120 – 293K, with minimum dielectric loss. The frequency dependence of dielectric loss shows a maximum in between 10 Hz and 1 kHz, confirms the extrinsic phenomena like interfacial polarization due to space charge accumulation at grain boundaries. Impedance spectroscopy is used to study the electrical behaviour of PFW in the frequency range from 100 to 1MHz and in the temperature range from 120 - 293 K. The frequency-dependent electrical data are analysed by impedance formalisms and shows the relaxation (conduction) mechanism in the sample. We suggest this low temperature sintered PFW is a suitable candidate for the multilayer ceramic capacitorsandrelated negative temperature coefficient of resistance type (NTCR) behavior like that of semiconductors.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Comparison between target margins derived from 4DCT scans and real-time tumor motion tracking: Insights from lung tumor patients treated with robotic radiosurgery

Purpose: A unique capability of the CyberKnife system is dynamic target tracking. However, not all patients are eligible for this approach. Rather, their tumors are tracked statically using the vertebral column for alignment. When using static tracking, the internal target volume (ITV) is delineated on the four-dimensional (4D) CT scan and an additional margin is added to account for setup uncertainty [planning target volume (PTV)]. Treatment margins are difficult to estimate due to unpredictable variations in tumor motion and respiratory pattern during the course of treatment. The inability to track the target and detect changes in respiratory characteristics might result in geographic misses and local tumor recurrences. The purpose of this study is to develop a method to evaluate the adequacy of ITV-to-PTV margins for patients treated in this manner. Methods: Data from 24 patients with lesions in the upper lobe (n = 12), middle lobe (n = 3), and lower lobe (n = 9) were included in this study. Each patient was treated with dynamic tracking and underwent 4DCT scanning at the time of simulation. Data including the 3D coordinates of the target over the course of treatment were extracted from the treatment log files and used to determine actual target motion in the superior–inferior (S–I), anterior–posterior (A–P), and left–right (L–R) directions. Different approaches were used to calculate anisotropic and isotropic margins, assuming that the tumor moves as a rigid body. Anisotropic margins were calculated by separating target motion in the three anatomical directions, and a uniform margin was calculated by shifting the gross tumor volume contours in the 3D space and by computing the percentage of overlap with the PTV. The analysis was validated by means of a theoretical formulation. Results: The three methods provided consistent results. A uniform margin of 4.5 mm around the ITV was necessary to assure 95% target coverage for 95% of the fractions included in the analysis. In the case of anisotropic margins, the expansion required in the S–I direction was larger (8.1 mm) than those in the L–R (4.9 mm) and A–P (4.5 mm) directions. This margin accounts for variations of target position within the same treatment fraction. Conclusions: The use of bony alignment for CyberKnife lung stereotactic body radiation therapy requires careful considerations, in terms of the potential for increased toxicity or local miss. Our method could be used by other centers to determine the adequacy of ITV-to-PTV margins for their patients.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Non-spectroscopic composition measurements of SrTiO 3 -La 0.7 Sr 0.3 MnO 3 multilayers using scanning convergent beam electron diffraction

The local atomic structure of a crystalline sample aligned along a zone axis can be probed with a focused electron probe, which produces a convergent beam electron diffraction pattern. The introduction of high speed direct electron detectors has allowed for experiments that can record a full diffraction pattern image at thousands of probe positions on a sample. By incoherently summing these patterns over crystalline unit cells, we demonstrate in this paper that in addition to crystal structure and thickness, we can also estimate the local composition of a perovskite superlattice sample. This is achieved by matching the summed patterns to a library of simulated diffraction patterns. Finally, this technique allows for atomic-scale chemical measurements without requiring a spectrometer or hardware aberration correction.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2020

Probing the local electronic structure of isovalent Bi atoms in InP

Cross-sectional scanning tunneling microscopy (X-STM) is used to experimentally study the influence of isovalent Bi atoms on the electronic structure of InP. In this work, we map the spatial pattern of the Bi impurity state, which originates from Bi atoms down to the sixth layer below the surface, in topographic, filled-state X-STM images on the natural {110} cleavage planes. The Bi impurity state has a highly anisotropic bowtielike structure and extends over several lattice sites. These Bi-induced charge redistributions extend along the $\langle$110$\rangle$ directions, which define the bowtielike structures we observe. Local tight-binding calculations reproduce the experimentally observed spatial structure of the Bi impurity state. In addition, the influence of the Bi atoms on the electronic structure is investigated in scanning tunneling spectroscopy measurements. These measurements show that Bi induces a resonant state in the valence band, which shifts the band edge toward higher energies. Furthermore, we show that the energetic position of the Bi-induced resonance and its influence on the onset of the valence band edge depend crucially on the position of the Bi atoms relative to the cleavage plane.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2025

Observation of Vortex Stripes in UTe 2

In conventional type-II superconductors, quantum vortices determine the magnetic response of the system and tend to form regular lattices. UTe 2 is a recently discovered heavy Fermion superconductor exhibiting many anomalous macroscopic behaviors, but whether it has a multicomponent order parameter remains open. Here, in this work, we study the vortices of UTe 2 by employing scanning superconducting quantum interference device microscopy. While a small out-of-plane magnetic field produces typical isolated vortices, a higher field generates vortex stripe patterns that evolve with the vortex density. The stripes form at different locations and along different directions in the surface plane when the field is along the b or c axis. The behavior is reproduced by our simulation based on an anisotropic two-component order parameter. This study shows that UTe 2 has a nontrivial disparity of multiple length scales, placing constraints on the multicomponent superconductivity.

UTe2↗