Chalk River Laboratories

About: Chalk River Laboratories is a based out in . It is known for research contribution in the topics: Neutron diffraction & Neutron scattering. The organization has 2297 authors who have published 2700 publications receiving 73287 citations.

Dynamic stripes and resonance in the superconducting and normal phases of YBa2Cu3O6.5 ortho-II superconductor

Abstract: We describe the relation between spin fluctuations and superconductivity in a highly ordered sample of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{6.5}$ using both polarized and unpolarized neutron inelastic scattering. The spin susceptibility in the superconducting phase exhibits one-dimensional incommensurate modulations at low energies, consistent with hydrodynamic stripes. With increasing energy the susceptibility curves upward to a commensurate, intense, well-defined, and asymmetric resonance at 33 meV with a precipitous high-energy cutoff. In the normal phase, which we show is gapless, the resonance remains surprisingly strong and persists clearly in Q scans and energy scans. Its similar asymmetric spectral form above ${T}_{c}=59\mathrm{K}$ suggests that incoherent superconducting pairing fluctuations are present in the normal state. On cooling, the resonance and the stripe modulations grow in well above ${T}_{c}$ below a temperature that is comparable to the pseudogap temperature where suppression occurs in local and low-momentum properties. The spectral weight that accrues to the resonance is largely acquired by transfer from suppressed low-energy fluctuations. We find the resonance to be isotropically polarized, consistent with a triplet carrying $\ensuremath{\sim}2.6%$ of the total spectral weight of the Cu spins in the planes.

Ferroelectric ordering in the relaxor P b ( M g 1 / 3 Nb 2 / 3 ) O 3 as evidenced by low-temperature phonon anomalies

Abstract: Neutron scattering measurements of the lowest-energy TO phonons in the relaxor $\mathrm{Pb}({\mathrm{Mg}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_{3}$ (PMN) are reported for $10l~Tl~750 \mathrm{K}.$ The soft mode, which is overdamped by the polar nanoregions below the Burns temperature ${T}_{d}=620 \mathrm{K},$ surprisingly recovers below 220 K. The square of the soft-mode energy $(\ensuremath{\Elzxh}{\ensuremath{\omega}}_{0}{)}^{2}$ increases linearly with decreasing temperature and is consistent with the behavior of a ferroelectric soft mode. At 10 K, $\ensuremath{\Elzxh}{\ensuremath{\omega}}_{0}$ reaches 11 meV, the same value observed in ferroelectric $\mathrm{Pb}({\mathrm{Zn}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_{3}$ at low T. An unusual broadening of the TA phonon starts at ${T}_{d}$ and disappears at 220 K, coincident with the recovery of the TO mode. These dynamics suggest that a well-developed ferroelectric state is established below 220 K.

Gapped itinerant spin excitations account for missing entropy in the hidden-order state of URu 2 Si 2

Abstract: Gapped itinerant spin excitations account for missing entropy in the hidden-order state of URu 2 Si 2

Spin freezing in the geometrically frustrated pyrochlore antiferromagnet Tb 2 Mo 2 O 7

Abstract: The magnetic metal ions in the cubic pyrochlore ${\mathrm{Tb}}_{2}$${\mathrm{Mo}}_{2}$${\mathrm{O}}_{7}$ form an infinite three-dimensional network of corner-sharing tetrahedra with a very high potential for frustration in the presence of antiferromagnetism. We have performed neutron scattering measurements which show short-range spatial correlations that develop continuously with decreasing temperature, while the characteristic time scale for the fluctuating moments decreases dramatically below ${\mathit{T}}_{\mathit{f}}$\ensuremath{\sim}25 K. Therefore, this pure material, which possess frustration that is purely geometrical in origin, displays a spin-glass state at low temperatures.