108 research outputs found
Quantum oscillations and a non-trivial Berry phase in the noncentrosymmetric superconductor BiPd
We report the measurements of de Haas-van Alphen (dHvA) oscillations in the
noncentrosymmetric superconductor BiPd. Several pieces of a complex multi-sheet
Fermi surface are identified, including a small pocket (frequency 40 T) which
is three dimensional and anisotropic. From the temperature dependence of the
amplitude of the oscillations, the cyclotron effective mass is (
0.1) . Further analysis showed a non-trivial -Berry phase is
associated with the 40 T pocket, which strongly supports the presence of
topological states in bulk BiPd and may result in topological superconductivity
due to the proximity coupling to other bands.Comment: 5 pages, 3 figure
Electrical anisotropy and coexistence of structural transitions and superconductivity in IrT e2
We report experimental investigations of the electrical transport, magnetic, and thermodynamic properties of IrTe2 single crystals. The resistivity, magnetization, and specific heat display anomalies at TS1≈283K,TS2≈167K, and Tc≈2.5K, corresponding to two structural and one superconducting phase transitions, respectively, demonstrating the coexistence of all of these transitions in high-quality stoichiometric samples. While there is little magnetic anisotropy, a large ab-plane (ρab) and c-axis (ρc) electrical resistivity ratio (ρc/ρab≈730 at T=4K) is observed. This two-dimensional (2D) electronic character is further reflected in the disparate temperature dependences of ρab and ρc, with ρab exhibiting a Fermi-liquid-like T2 dependence below ∼25K, while ρc deviates significantly from this standard metallic behavior. In contrast, the magnetization is almost isotropic and negative over a wide temperature range. This can be explained by larger diamagnetism induced by electronic structure reconstruction as probed by the Hall effect and smaller positive contribution from itinerant electrons due to a low density of states (DOS) at the Fermi level. A small electronic specific heat coefficient with γ≈1.8mJ/molK2 confirms this assertion. This implies that IrTe2 is a weakly coupled superconductor. The connection between the superconductivity and the two structural transitions is discussed
High pO2 Floating Zone Crystal Growth of the Perovskite Nickelate PrNiO3
Single crystals of PrNiO3 were grown under an oxygen pressure of 295 bar
using a unique high-pressure optical-image floating zone furnace. The crystals,
with volume in excess of 1 mm3, were characterized structurally using single
crystal and powder X-ray diffraction. Resistivity, specific heat, and magnetic
susceptibility were measured, all of which evidenced an abrupt, first order
metal-insulator transition (MIT) at ~130 K, in agreement with previous
literature reports on polycrystalline specimens. Temperature-dependent single
crystal diffraction was performed to investigate changes through the MIT. Our
study demonstrates the opportunity space for high fugacity, reactive
environments for single crystal growth specifically of perovskite nickelates
but more generally to correlated electron oxides.Comment: 19 pages, 6 figures, Supporting Information include
Synthesis and characterization of a series of nickel(II) alkoxide precursors and their utility for Ni(0) nanoparticle production
A series of nickel(ii) aryloxide ([Ni(OAr)2(py)x]) precursors was synthesized from an amide-alcohol exchange using [Ni(NR2)2] in the presence of pyridine (py). The H-OAr selected were the mono- and di-ortho-substituted 2-alkyl phenols: alkyl = methyl (H-oMP), iso-propyl (H-oPP), tert-butyl (H-oBP) and 2,6-di-alkyl phenols (alkyl = di-iso-propyl (H-DIP), di-tert-butyl (H-DBP), di-phenyl (H-DPhP)). The crystalline products were solved as solvated monomers and structurally characterized as [Ni(OAr)2(py)x], where x = 4: OAr = oMP (1), oPP (2); x = 3: OAr = oBP (3), DIP (4); x = 2: OAr = DBP (5), DPhP (6). The excited states (singlet or triplet) and various geometries of 1-6 were identified by experimental UV-vis and verified by computational modeling. Magnetic susceptibility of the representative compound 4 was fit to a Curie Weiss model that yielded a magnetic moment of 4.38(3)μB consistent with a Ni2+ center. Compounds 1 and 6 were selected for decomposition studied under solution precipitation routes since they represent the two extremes of coordination. The particle size and crystalline structure were characterized using transmission electron microscopy (TEM) and powder X-ray diffraction (PXRD). The materials isolated from 1 and 6 were found by TEM to form irregular shape nanomaterials (8-15 nm), which by PXRD were found to be Ni0 hcp (PDF: 01-089-7129) and fcc (PDF: 01-070-0989), respectively
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