1,238 research outputs found
Random anisotropy disorder in superfluid 3He-A in aerogel
The anisotropic superfluid 3He-A in aerogel provides an interesting example
of a system with continuous symmetry in the presence of random anisotropy
disorder. Recent NMR experiments allow us to discuss two regimes of the
orientational disorder, which have different NMR properties. One of them, the
(s)-state, is identified as the pure Larkin-Imry-Ma state. The structure of
another state, the (f)-state, is not very clear: probably it is the
Larkin-Imry-Ma state contaminated by the network of the topological defects
pinned by aerogel.Comment: JETP Lett. style, 6 pages, no figures, discussion extended,
references added, version to be published in JETP Letter
Stable Spin Precession at one Half of Equilibrium Magnetization in Superfluid 3He-B
New stable modes of spin precession have been observed in superfluid 3He-B.
These dynamical order parameter states include precession with a magnetization
S=pS_{eq} which is different from the equilibrium value S_{eq}. We have
identified modes with p=1, 1/2 and \approx 0. The p=1/2 mode is the second
member of phase correlated states of a spin superfluid. The new states can be
excited in the temperature range 1-T/T_c \lesssim 0.02 where the energy
barriers between the different local minima of the spin-orbit energy are small.
They are stable in CW NMR due to low dissipation close to T_c.Comment: submitted to Physical Review Letters, 4 pages, revtex, 4 Figures in
ftp://boojum.hut.fi/pub/publications/lowtemp/LTL-96005.p
Nonmonotonic magnetoresistance of a two-dimensional viscous electron-hole fluid in a confined geometry
Ultra-pure conductors may exhibit hydrodynamic transport where the collective
motion of charge carriers resembles the flow of a viscous fluid. In a confined
geometry (e.g., in ultra-high quality nanostructures) the electronic fluid
assumes a Poiseuille-like flow. Applying an external magnetic field tends to
diminish viscous effects leading to large negative magnetoresistance. In
two-component systems near charge neutrality the hydrodynamic flow of charge
carriers is strongly affected by the mutual friction between the two
constituents. At low fields, the magnetoresistance is negative, however at high
fields the interplay between electron-hole scattering, recombination, and
viscosity results in a dramatic change of the flow profile: the
magnetoresistance changes its sign and eventually becomes linear in very high
fields. This novel non-monotonic magnetoresistance can be used as a fingerprint
to detect viscous flow in two-component conducting systems.Comment: 10 pages, 8 figure
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