10,726 research outputs found
BCS - BEC crossover and quantum hydrodynamics in p-wave superfluids with a symmetry of the A1 - phase
We solve the Leggett equations for the BCS - BEC crossover in the three
dimension resonance p-wave superfluid with the symmetry of the A1 - phase. We
calculate the sound velocity, the normal density, and the specific heat for the
BCS-domain (\mu > 0), BEC-domain (\mu < 0), and close to important point \mu =
0 in 100% polarized case. We find the indications of quantum phase - transition
close to the point \mu(T = 0) = 0. Deep in the BCS and BEC-domains the
crossover ideas of Leggett and Nozieres, Schmitt-Rink work pretty well. We
discuss the spectrum of orbital waves, the paradox of intrinsic angular
momentum and complicated problem of chiral anomaly in the BCS A1 - phase at T =
0. We present two different approaches to a chiral anomaly: one based on
supersymmetric hydrodynamics, another one on the formal analogy with the Dirac
equation in quantum electrodynamics. We evaluate the damping of nodal fermions
due to different decay processes in superclean case at T = 0 and find that we
are in a ballistic regime \omega\tau >> 1. We propose to use aerogel or
nonmagnetic impurities to reach hydrodynamic regime \omega\tau<< 1 at T = 0. We
discuss the concept of the spectral flow and exact cancellations between
time-derivatives of anomalous and quasiparticle currents in the equation for
the total linear momentum conservation. We propose to derive and solve the
kinetic equation for the nodal quasiparticles both in the hydrodynamic and in
the ballistic regimes to demonstrate this cancellation explicitly. We briefly
discuss the role of the other residual interactions different from damping and
invite experimentalists to measure the spectrum and damping of orbital waves in
A-phase of 3He at low temperatures.Comment: 14 pages, 10 figure
Probing New Physics From CP Violation in Radiative B Decays
When new CP-violating interactions are dominated by flavor changing neutral
particle exchanges, that may occur in many extensions of the standard model. We
examine a type 3 two Higgs doublet model and find that direct CP asymmetries
can be as large as about 25% . Time-dependent and time-integrated
mixing-induced CP asymmetries up to 85 and 40 %, respectively, are possible
without conflict with other constraints. It mainly requirs an enhanced
chromo-magnetic dipole decay to be close to the present experimental
bound.Comment: 7 pages, latex, no figure
Quantum Glassiness
Describing matter at near absolute zero temperature requires understanding a
system's quantum ground state and the low energy excitations around it, the
quasiparticles, which are thermally populated by the system's contact to a heat
bath. However, this paradigm breaks down if thermal equilibration is
obstructed. This paper presents solvable examples of quantum many-body
Hamiltonians of systems that are unable to reach their ground states as the
environment temperature is lowered to absolute zero. These examples, three
dimensional generalizations of quantum Hamiltonians proposed for topological
quantum computing, 1) have no quenched disorder, 2) have solely local
interactions, 3) have an exactly solvable spectrum, 4) have topologically
ordered ground states, and 5) have slow dynamical relaxation rates akin to
those of strong structural glasses.Comment: 4 page
Double-exchange model: phase separation versus canted spins
We study the competition between different possible ground states of the
double-exchange model with strong ferromagnetic exchange interaction between
itinerant electrons and local spins. Both for classical and quantum treatment
of the local spins the homogeneous canted state is shown to be unstable against
a phase separation. The conditions for the phase separation into the mixture of
the antiferromagnetic and ferromagnetic/canted states are given. We also
discuss another possible realization of the phase-separated state:
ferromagnetic polarons embedded into an antiferromagnetic surrounding. The
general picture of a percolated state, which emerges from these considerations,
is discussed and compared with results of recent experiments on doped
manganaties.Comment: 10 pages, revtex, modified text and 2 new figure
Phase separation in systems with charge ordering
A simple model of charge ordering is considered. It is shown explicitly that
at any deviation from half-filling () the system is unstable with
respect to phase separation into charge ordered regions with and
metallic regions with smaller electron or hole density. Possible structure of
this phase-separated state (metallic droplets in a charge-ordered matrix)is
discussed. The model is extended to account for the strong Hund-rule onsite
coupling and the weaker intersite antiferromagnetic exchange. An analysis of
this extended model allows us to determine the magnetic structure of the
phase-separated state and to reveal the characteristic features of manganites
and other substances with charge ordering.Comment: 9 pages, revte
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