263 research outputs found
Feedback Control and Characterization of a Microcantilever Using Optical Radiation Pressure
We describe a method for feedback-regulation of a microcantilever's response
using optical radiation pressure. One laser measures the position of the
cantilever and another laser applies a force that is a phase-shifted function
of that position. The force is due solely to the momentum of the photons in the
laser. The feedback changes the microcantilever's effective quality factor Qeff
and effective temperature Teff. Reduction of both Qeff and Teff by more than a
factor of 15 is demonstrated. Additionally, we suggest a method for
determination of a microcantilever's spring constant using the known force
exerted on it by radiation pressure.Comment: 10 pages, 3 figures. Updated acknowledgements and used smaller file
format for Figure
Hidden quasi one-dimensional superconductivity in SrRuO
Using an asymptotically exact weak coupling analysis of a multi-orbital
Hubbard model of the electronic structure of \SRO, we show that the interplay
between spin and charge fluctuations leads unequivocally to triplet pairing
which originates in the quasi-one dimensional bands. The resulting
superconducting state spontaneously breaks time-reversal symmetry and is of the
form with sharp gap minima and a d-vector
that is only {\it weakly} pinned. The supercondutor is topologically {\it
trivial} and hence lacks robust chiral Majorana fermion modes along the
boundary. The absence of topologically protected edge modes could explain the
surprising absence of experimentally detectable edge currents in this system.Comment: 5 pages, 3 figure
STM Studies of TbTe3: Evidence for a fully Incommensurate Charge Density Wave
We observe unidirectional charge density wave ordering on the cleaved surface
of TbTe3 with a Scanning Tunneling Microscope at ~6 K. The modulation
wave-vector q_{CDW} as determined by Fourier analysis is 0.71 +/- 0.02 * 2
pi/c. (Where c is one edge of the in-plane 3D unit cell.) Images at different
tip-sample voltages show the unit cell doubling effects of dimerization and the
layer below. Our results agree with bulk X-ray measurements, with the addition
of ~(1/3) * 2 pi/a ordering perpendicular to the CDW. Our analysis indicates
that the CDW is incommensurate.Comment: 4 pages, 4 figure
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