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Locally addressable tunnel barriers within a carbon nanotube
We report the realization and characterization of independently controllable
tunnel barriers within a carbon nanotube. The nanotubes are mechanically bent
or kinked using an atomic force microscope, and top gates are subsequently
placed near each kink. Transport measurements indicate that the kinks form
gate-controlled tunnel barriers, and that gates placed away from the kinks have
little or no effect on conductance. The overall conductance of the nanotube can
be controlled by tuning the transmissions of either the kinks or the
metal-nanotube contacts.Comment: related papers at http://marcuslab.harvard.ed
Spinor Fields and Symmetries of the Spacetime
In the background of a stationary black hole, the "conserved current" of a
particular spinor field always approaches the null Killing vector on the
horizon. What's more, when the black hole is asymptotically flat and when the
coordinate system is asymptotically static, then the same current also
approaches the time Killing vector at the spatial infinity. We test these
results against various black hole solutions and no exception is found. The
spinor field only needs to satisfy a very general and simple constraint.Comment: 19 page
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