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1.
Adv Mater ; 34(35): e2202971, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35817958

RESUMO

Devices with tunable magnetic noncollinearity are important components of superconducting electronics and spintronics, but they typically require epitaxial integration of several complex materials. The spin-polarized neutron reflectometry measurements on La1-x Srx MnO3 homojunction arrays with modulated Sr concentration reported herein have led to the discovery of magnetic fan structures with highly noncollinear alignment of Mn spins and an emergent periodicity twice as large as the array's unit cell. The neutron data show that these magnetic superstructures can be fully long-range ordered, despite the gradual modulation of the doping level created by charge transfer and chemical intermixing. The degree of noncollinearity can be effectively adjusted by low magnetic fields. Notwithstanding their chemical and structural simplicity, oxide homojunctions thus show considerable promise as a platform for tunable complex magnetism and as a powerful design element of spintronic devices.

2.
Proc Natl Acad Sci U S A ; 118(30)2021 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-34301905

RESUMO

We have used atomic layer-by-layer oxide molecular beam epitaxy to grow epitaxial thin films of [Formula: see text] with x up to 0.5, greatly exceeding the solubility limit of Ca in bulk systems ([Formula: see text]). A comparison of the optical conductivity measured by spectroscopic ellipsometry to prior predictions from dynamical mean-field theory demonstrates that the hole concentration p is approximately equal to x. We find superconductivity with [Formula: see text] of 15 to 20 K up to the highest doping levels and attribute the unusual stability of superconductivity in [Formula: see text] to the nearly identical radii of La and Ca ions, which minimizes the impact of structural disorder. We conclude that careful disorder management can greatly extend the "superconducting dome" in the phase diagram of the cuprates.

3.
Orthopedics ; 44(6): e729-e734, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34618642

RESUMO

The distal radioulnar joint (DRUJ) is stabilized by the bony anatomy of the contact surfaces. The authors analyzed the morphologic characteristics and radiologic parameters at the sigmoid notch of patients with a peripheral triangular fibrocartilage complex (TFCC) tear compared with asymptomatic patients. Preoperative axial computed tomography scans were reviewed for 76 wrists with peripheral TFCC injuries, including foveal avulsion, and 76 wrists of age- and sex-matched control subjects. The authors used axial computed tomography scans of the DRUJ to classify the patients into 4 groups according to the type of sigmoid notch, namely, flat face, ski-slope, C-type, and S-type. They also measured the tilting angle, depth, width of the sigmoid notch, and radioulnar ratio (RUR). Statistical analyses were performed with the chi-square test or paired t test (P<.05). The mean proportions of flat face, ski-slope, C-type, and S-type sigmoid notches among patients with peripheral TFCC injuries were 42%, 22%, 29%, and 7%, respectively, whereas those for the control group were 33%, 1%, 65%, and 1%, respectively (P<.05). The tilting angle was lower (TFCC injury, 84.5°; control, 86.2°; P<.05) and the RUR was significantly higher (TFCC injury, 0.67; control, 0.56) in the TFCC group, particularly for men (P<.05). Depth (TFCC injury, 1.0 mm; control, 1.3 mm; P>.05) and width (TFCC injury, 14.8 mm; control, 14.5 mm; P>.05) were similar between the groups. Patients with ski-slope or dorsally tilted sigmoid notches may be at greater risk for peripheral TFCC injuries. [Orthopedics. 2021;44(6):e729-e734.].


Assuntos
Doenças das Cartilagens , Fibrocartilagem Triangular , Traumatismos do Punho , Humanos , Masculino , Rádio (Anatomia) , Fibrocartilagem Triangular/diagnóstico por imagem , Traumatismos do Punho/diagnóstico por imagem , Traumatismos do Punho/cirurgia , Articulação do Punho
4.
ACS Nano ; 15(10): 16228-16235, 2021 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-34592093

RESUMO

Strain engineering of complex oxide heterostructures has provided routes to explore the influence of the local perturbations to the physical properties of the material. Due to the challenge of disentangling intrinsic and extrinsic effects at oxide interfaces, the combined effects of epitaxial strain and charge transfer mechanisms have been rarely studied. Here, we reveal the local charge distribution in manganite slabs by means of high-resolution electron microscopy and spectroscopy via investigating how the strain locally alters the electronic and magnetic properties of La0.5Sr0.5MnO3-La2CuO4 heterostructures. The charge rearrangement results in two different magnetic phases: an interfacial ferromagnetically reduced layer and an enhanced ferromagnetic metallic region away from the interfaces. Further, the magnitude of the charge redistribution can be controlled via epitaxial strain, which further influences the macroscopic physical properties in a way opposed to strain effects reported on single-phase films. Our work highlights the important role played by epitaxial strain in determining the spatial distribution of microscopic charge and spin interactions in manganites and provides a different perspective for engineering interface properties.

5.
Beilstein J Nanotechnol ; 11: 1254-1263, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32874825

RESUMO

We have investigated the structural, magnetic and superconduction properties of [Nb(1.5 nm)/Fe(x)]10 superlattices deposited on a thick Nb(50 nm) layer. Our investigation showed that the Nb(50 nm) layer grows epitaxially at 800 °C on the Al2O3(1-102) substrate. Samples grown at this condition possess a high residual resistivity ratio of 15-20. By using neutron reflectometry we show that Fe/Nb superlattices with x < 4 nm form a depth-modulated FeNb alloy with concentration of iron varying between 60% and 90%. This alloy has weak ferromagnetic properties. The proximity of this weak ferromagnetic layer to a thick superconductor leads to an intermediate phase that is characterized by a suppressed but still finite resistance of structure in a temperature interval of about 1 K below the superconducting transition of thick Nb. By increasing the thickness of the Fe layer to x = 4 nm the intermediate phase disappears. We attribute the intermediate state to proximity induced non-homogeneous superconductivity in the structure.

6.
Nat Commun ; 11(1): 1793, 2020 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-32286291

RESUMO

In high-energy physics, the Higgs field couples to gauge bosons and fermions and gives mass to their elementary excitations. Experimentally, such couplings can be inferred from the decay product of the Higgs boson, i.e., the scalar (amplitude) excitation of the Higgs field. In superconductors, Cooper pairs bear a close analogy to the Higgs field. Interaction between the Cooper pairs and other degrees of freedom provides dissipation channels for the amplitude mode, which may reveal important information about the microscopic pairing mechanism. To this end, we investigate the Higgs (amplitude) mode of several cuprate thin films using phase-resolved terahertz third harmonic generation (THG). In addition to the heavily damped Higgs mode itself, we observe a universal jump in the phase of the driven Higgs oscillation as well as a non-vanishing THG above Tc. These findings indicate coupling of the Higgs mode to other collective modes and potentially a nonzero pairing amplitude above Tc.

7.
Phys Rev Lett ; 115(22): 226402, 2015 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-26650312

RESUMO

Barium bismuth oxide (BaBiO_{3}) is the end member of two families of high-T_{c} superconductors, i.e., BaPb_{1-x}Bi_{x}O_{3} and Ba_{1-x}K_{x}BiO_{3}. The undoped parent compound is an insulator, exhibiting a charge density wave that is strongly linked to a static breathing distortion in the oxygen sublattice of the perovskite structure. We report a comprehensive spectroscopic and x-ray diffraction study of BaBiO_{3} thin films, showing that the minimum film thickness required to stabilize the breathing distortion and charge density wave is ≈11 unit cells, and that both phenomena are suppressed in thinner films. Our results constitute the first experimental observation of charge density wave suppression in bismuthate compounds without intentionally introducing dopants.

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