63 research outputs found
From Fermi Arcs to the Nodal Metal: Scaling of the Pseudogap with Doping and Temperature
The pseudogap phase in the cuprates is a most unusual state of matter: it is
a metal, but its Fermi surface is broken up into disconnected segments known as
Fermi arcs. Using angle resolved photoemission spectroscopy, we show that the
anisotropy of the pseudogap in momentum space and the resulting arcs depend
only on the ratio T/T*(x), where T*(x) is the temperature below which the
pseudogap first develops at a given hole doping x. In particular, the arcs
collapse linearly with T/T* and extrapolate to zero extent as T goes to 0. This
suggests that the T = 0 pseudogap state is a nodal liquid, a strange metallic
state whose gapless excitations are located only at points in momentum space,
just as in a d-wave superconductor.Comment: to appear, Nature Physics (July 2006
Thermal Evolution of the Proton Irradiated Structure in Tungsten–5 wt% Tantalum
We have monitored the thermal evolution of the proton irradiated structure of W–5 wt% Ta alloy by in-situ annealing in a transmission electron microscope at fusion reactor temperatures of 500–1300 °C. The interstitial-type a/2 dislocation loops emit self-interstitial atoms and glide to the free sample surface during the early stages of annealing. The resultant vacancy excess in the matrix originates vacancy-type a/2 dislocation loops that grow by loop and vacancy absorption in the temperature range of 600–900 °C. Voids form at 1000 °C, by either vacancy absorption or loop collapse, and grow progressively up to 1300 °C. Tantalum delays void formation by a vacancy-solute trapping mechanism
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