6,250 research outputs found
Magneto-Acoustic Spectroscopy in Superfluid 3He-B
We have used the recently discovered acoustic Faraday effect in superfluid
3He to perform high resolution spectroscopy of an excited state of the
superfluid condensate. With acoustic cavity interferometry we measure the
rotation of the plane of polarization of a transverse sound wave propagating in
the direction of magnetic field from which we determine the Zeeman energy of
the excited state. We interpret the Lande g-factor, combined with the
zero-field energies of the state, using the theory of Sauls and Serene to
calculate the strength of f -wave interactions in 3He.Comment: 4 pages, 5 figures, submitted to PRL, Aug 30th, 200
Graded Lie algebras with finite polydepth
If A is a graded connected algebra then we define a new invariant, polydepth
A, which is finite if for some A-module M of at most
polynomial growth. Theorem 1: If f : X \to Y is a continuous map of finite
category, and if the orbits of H_*(\Omega Y) acting in the homology of the
homotopy fibre grow at most polynomially, then H_*(\Omega Y) has finite
polydepth. Theorem 2: If L is a graded Lie algebra and polydepth UL is finite
then either L is solvable and UL grows at most polynomially or else for some
integer d and all r, , some
Nonlinear field-dependence and f-wave interactions in superfluid 3He
We present results of transverse acoustics studies in superfluid ^{3}He-B at
fields up to 0.11 T. Using acoustic cavity interferometry, we observe the
Acoustic Faraday Effect for a transverse sound wave propagating along the
magnetic field, and we measure Faraday rotations of the polarization as large
as 1710^{\circ}. We use these results to determine the Zeeman splitting of the
Imaginary Squashing mode, an order parameter collective mode with total angular
momentum J=2. We show that the pairing interaction in the f-wave channel is
attractive at a pressure of P=6 bar. We also report nonlinear field dependence
of the Faraday rotation at frequencies substantially above the mode frequency
not accounted for in the theory of the transverse acoustic dispersion relation
formulated for frequencies near the mode. Consequently, we have identified the
region of validity of the theory allowing us to make corrections to the
analysis of Faraday rotation experiments performed in earlier work.Comment: 7 pages, 5 figure
Acoustic Spectroscopy of Superfluid 3He in Aerogel
We have designed an experiment to study the role of global anisotropic
quasiparticle scattering on the dirty aerogel superfluid 3He system. We observe
significant regions of two stable phases at temperatures below the superfluid
transition at a pressure of 25 bar for a 98% aerogel.Comment: 2 pages, 2 figures, accepted for publication in proceedings of Low
Temperature Conference 2
Cubic Dresselhaus Spin-Orbit Coupling in 2D Electron Quantum Dots
We study effects of the oft-neglected cubic Dresselhaus spin-orbit coupling
(i.e., ) in GaAs/AlGaAs quantum dots. Using a semiclassical
billiard model, we estimate the magnitude of the spin-orbit induced avoided
crossings in a closed quantum dot in a Zeeman field. Using these results,
together with previous analyses based on random matrix theory, we calculate
corresponding effects on the conductance through an open quantum dot. Combining
our results with an experiment on conductance through an 8 um^2 quantum dot [D
M Zumbuhl et al., Phys. Rev. B 72, 081305 (2005)] suggests that 1) the GaAs
Dresselhaus coupling constant, , is approximately 9 eVA^3,
significantly less than the commonly cited value of 27.5 eVA^3 and 2) the
majority of the spin-flip component of spin-orbit coupling can come from the
cubic Dresselhaus term.Comment: 4 pages plus supplementary tabl
- …