30 research outputs found
Se and Cu NMR studies of the electronic correlations in CuTiSe ()
We report Se and Cu nuclear magnetic resonance (NMR)
investigation on the charge-density-wave (CDW) superconductor CuTiSe
( and 0.07). At high magnetic fields where superconductivity is
suppressed, the temperature dependence of Se and Cu spin-lattice
relaxation rates 1/T_{1}^{77}1/T_{1}$
vs \emph{T} increases with the Cu doping. This can be described by a modified
Korringa relation which suggests the significance of electronic correlations
and the Se 4\emph{p}- and Ti 3\emph{d}-band contribution to the density of
states at the Fermi level in the studied compounds.Comment: Revised manuscript. Submitted to Journal of Physics: Condensed Matte
Flux quanta driven by high-density currents in low-impurity V3Si and LuNi2B2C: free flux flow and flux-core size effect
High density direct currents (DC) are used to drive flux quanta via the
Lorentz force towards a highly ordered "free flux flow" (FFF) dynamic state,
made possible by the weak-pinning environment of high-quality, single-crystal
samples of two low-Tc superconducting compounds, V3Si and LuNi2B2C. We report
the effect of the magnetic field-dependent fluxon core size on flux flow
resistivity rho_f. Much progress has been made in minimizing the technical
challenges associated with the use of high currents. Attainment of a FFF phase
is indicated by the saturation at highest currents of flux-flow dissipation
levels that are well below the normal state resistance and have field-dependent
values. The field dependence of the corresponding rho_f is shown to be
consistent with a prediction based on a model for the decrease of flux core
size at higher fields in weak-coupling BCS s-wave materials.Comment: More empirical treatment of the magnetoresistive correction of V3Si
data by additional measurement and analysis (involving two new coauthors,
Favreau and Henderson). End result is the same, making for a stronger
manuscrip
1H and 195Pt NMR Study of the Parallel Two-Chain Compound Per2[Pt(mnt)2]
1H and 195Pt NMR are used to probe the spin ½ anion chain in the quasi-one-dimensional conductor Per2[Pt(mnt)2], which exhibits nearly simultaneous charge density wave (CDW) and spin-Peierls (SP) transitions at low temperatures (Tc ~ 8 K). Below Tc the [Pt(mnt)2] chain forms a spin-singlet state that is evident in 1H NMR spectra and spin relaxation (1/T1) rates; however minority unpaired Pt spins may remain in the SP ground state. With increasing magnetic field, the SP and CDW order parameters decrease in unison, indicating they are coupled up to a critical field Bc ~ 20 T. Above Bc, the spin singlet evolves into a spin-polarized configuration. The 195Pt NMR signals vanish as either Tc or Bc are approached from within the SP ground state, suggesting the hyperfine field of the Pt nucleus is significantly stronger than at the proton sites. Simulations yield a consistent picture of the angular, temperature, and magnetic field-dependent spectral features
Flux quanta driven by high-density currents in low-impurity V3Si and LuNi2B2C: Free flux flow and fluxon-core size effect
High-density direct currents are used to drive flux quanta via the Lorentz force toward a highly ordered "free flux flow" (FFF) dynamic state, made possible by the weak-pinning environment of high-quality, single-crystal samples of two low-T-c superconducting compounds, V3Si and LuNi2B2C. We report the effect of the magnetic field-dependent fluxon-core size on flux flow resistivity rho(f). Much progress has been made in minimizing the technical challenges associated with the use of high currents. Attainment of a FFF phase is indicated by the saturation at highest currents of flux flow dissipation levels that are well below the normal-state resistance and have field-dependent values. The field dependence of the corresponding rho(f) is shown to be consistent with a prediction based on a model for the decrease of fluxon-core size at higher fields in weak-coupling BCS s-wave materials.This article is published as Gapud, Albert A., S. Moraes, R. P. Khadka, P. Favreau, C. Henderson, P. C. Canfield, V. G. Kogan et al. "Flux quanta driven by high-density currents in low-impurity V 3 Si and LuNi 2 B 2 C: Free flux flow and fluxon-core size effect." Physical Review B 80, no. 13 (2009): 134524.
DOI: 10.1103/PhysRevB.80.134524.
Copyright 2009 American Physical Society.
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