340 research outputs found
Mean Field Description of the Fractional Quantum Hall Effect Near
The nature of Mean Field Solutions to the Equations of Motion of the
Chern--Simons Landau--Ginsberg (CSLG) description of the Fractional Quantum
Hall Effect (FQHE) is studied. Beginning with the conventional description of
this model at some chemical potential and magnetic field
corresponding to a ``special'' filling fraction
() we show that a deviation of in a finite range
around does not change the Mean Field solution and thus the mean
density of particles in the model. This result holds not only for the lowest
energy Mean Field solution but for the vortex excitations as well. The vortex
configurations do not depend on in a finite range about in this
model. However when ) the
lowest energy Mean Field solution describes a condensate of vortices (or
antivortices). We give numerical examples of vortex and antivortex
configurations and discuss the range of and over which the system
of vortices is dilute.Comment: Revtex document; 12 pages and 4 postscript figures in a fil
Quantum spin configurations in Tb2Ti2O7
Low energy collective angular momentum states of the Tb3+ ions in Tb2Ti2O7
are classified according to the irreducible representations of the octahedral
point group. Degeneracy lifting due to the exchange interaction is discussed.
Diffuse neutron scattering intensity patterns are calculated for each
collective angular momentum state and the ground state is inferred by comparing
to experiment.Comment: 5 pages, 1 colour figure. Slight corrections and additions to text
and figur
Structural distortion and the spin liquid state in Tb2Ti2O7
It is shown that a k=0, A_{2u} distortion of the terbium tetrahedral network
in Tb2Ti2O7 accounts for the apparent isolation of single tetrahedra as seen in
neutron scattering studies. Single tetrahedron collective spin states, rather
than individual spins, account for the main features of the spin liquid state,
namely, fluctuating local moments and the absence of long range order. Singlet
and doublet collective spin ground states are considered. An effective
interaction between tetrahedra on the fcc lattice is derived and found to be
weak and anisotropic.Comment: 5 page
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