19,165 research outputs found
Magnetic domain formation in itinerant metamagnets
We examine the effects of long-range dipolar forces on metamagnetic
transitions and generalize the theory of Condon domains to the case of an
itinerant electron system undergoing a first-order metamagnetic transition. We
demonstrate that within a finite range of the applied field, dipolar
interactions induce a spatial modulation of the magnetization in the form of
stripes or bubbles. Our findings are consistent with recent observations in the
bilayer ruthenate SrRuO.Comment: 4 pages, 3 figures, minor changes, references adde
Superconductivity generated by coupling to a Cooperon in a 2-dimensional array of 4-leg Hubbard ladders
Starting from an array of four-leg Hubbard ladders weakly doped away from
half-filling and weakly coupled by inter-ladder tunneling, we derive an
effective low energy model which contains a partially truncated Fermi surface
and a well defined Cooperon excitation formed by a bound pair of holes. An
attractive interaction in the Cooper channel is generated on the Fermi surface
through virtual scattering into the Cooperon state. Although the model is
derived in the weak coupling limit of a four-leg ladder array, an examination
of exact results on finite clusters for the strong coupling t-J model suggests
the essential features are also present for a strong coupling Hubbard model on
a square lattice near half-filling.Comment: 20 pages, 4 figure
Development of a phase-change thermal storage system using modified anhydrous sodium hydroxide for solar electric power generation
A thermal storage system for use in solar power electricity generation was investigated analytically and experimentally. The thermal storage medium is principally anhydrous NaOH with 8% NaNO3 and 0.2% MnO2. Heat is charged into storage at 584 K and discharged from storage at 582 K by Therminol-66. Physical and thermophysical properties of the storage medium were measured. A mathematical simulation and computer program describing the operation of the system were developed. A 1/10 scale model of a system capable of storing and delivering 3.1 x 10 to the 6th power kJ of heat was designed, built, and tested. Tests included steady state charging, discharging, idling, and charge-discharge conditions simulating a solar daily cycle. Experimental data and computer-predicted results are correlated. A reference design including cost estimates of the full-size system was developed
Random wave functions and percolation
Recently it was conjectured that nodal domains of random wave functions are
adequately described by critical percolation theory. In this paper we
strengthen this conjecture in two respects. First, we show that, though wave
function correlations decay slowly, a careful use of Harris' criterion confirms
that these correlations are unessential and nodal domains of random wave
functions belong to the same universality class as non critical percolation.
Second, we argue that level domains of random wave functions are described by
the non-critical percolation model.Comment: 13 page
Magnon Dispersion in the Field-Induced Magnetically Ordered Phase of TlCuCl3
The magnetic properties of the interacting dimer system TlCuCl3 are
investigated within a bond-operator formulation. The observed field-induced
staggered magnetic order perpendicular to the field is described as a Bose
condensation of magnons which are linear combinations of dimer singlet and
triplet modes. This technique accounts for the magnetization curve and for the
field dependence of the magnon dispersion curves observed by high-field neutron
scattering measurements.Comment: 4 pages, 4 figures, REVTeX
Probabilistic state preparation of a single molecular ion by projection measurement
We show how to prepare a single molecular ion in a specific internal quantum
state in a situation where the molecule is trapped and sympathetically cooled
by an atomic ion and where its internal degrees of freedom are initially in
thermal equilibrium with the surroundings. The scheme is based on conditional
creation of correlation between the internal state of the molecule and the
translational state of the collective motion of the two ions, followed by a
projection measurement of this collective mode by atomic ion shelving
techniques. State preparation in a large number of internal states is possible.Comment: 4 pages, 2 figures, 2 table
Molecular heat pump for rotational states
In this work we investigate the theory for three different uni-directional
population transfer schemes in trapped multilevel systems which can be utilized
to cool molecular ions. The approach we use exploits the laser-induced coupling
between the internal and motional degrees of freedom so that the internal state
of a molecule can be mapped onto the motion of that molecule in an external
trapping potential. By sympathetically cooling the translational motion back
into its ground state the mapping process can be employed as part of a cooling
scheme for molecular rotational levels. This step is achieved through a common
mode involving a laser-cooled atom trapped alongside the molecule. For the
coherent mapping we will focus on adiabatic passage techniques which may be
expected to provide robust and efficient population transfers. By applying
far-detuned chirped adiabatic rapid passage pulses we are able to achieve an
efficiency of better than 98% for realistic parameters and including
spontaneous emission. Even though our main focus is on cooling molecular
states, the analysis of the different adiabatic methods has general features
which can be applied to atomic systems
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