8,545 research outputs found
Quantum insulating states of F=2 cold atoms in optical lattices
In this Letter we study various spin correlated insulating states of F=2 cold
atoms in optical lattices. We find that the effective spin exchange interaction
due to virtual hopping contains an {\em octopole} coupling between two
neighboring lattice sites. Depending on scattering lengths and numbers of
particles per site the ground states are either rotationally invariant dimer or
trimer Mott insulators or insulating states with various spin orders. Three
spin ordered insulating phases are ferromagnetic, cyclic and nematic Mott
insulators. We estimate the phase boundaries for states with different numbers
of atoms per lattice site.Comment: 4 pages, 1 figure include
Adiabatic Connection for Strictly-Correlated Electrons
Modern density functional theory (DFT) calculations employ the Kohn-Sham (KS)
system of non-interacting electrons as a reference, with all complications
buried in the exchange-correlation energy (Exc). The adiabatic connection
formula gives an exact expression for Exc. We consider DFT calculations that
instead employ a reference of strictly-correlated electrons. We define a
"decorrelation energy" that relates this reference to the real system, and
derive the corresponding adiabatic connection formula. We illustrate this
theory in three situations, namely the uniform electron gas, Hooke's atom, and
the stretched hydrogen molecule. The adiabatic connection for
strictly-correlated electrons provides an alternative perspective for
understanding density functional theory and constructing approximate
functionals.Comment: 4 figures, has been published in J. Chem. Phy
Domain walls in gapped graphene
The electronic properties of a particular class of domain walls in gapped
graphene are investigated. We show that they can support mid-gap states which
are localized in the vicinity of the domain wall and propagate along its
length. With a finite density of domain walls, these states can alter the
electronic properties of gapped graphene significantly. If the mid-gap band is
partially filled,the domain wall can behave like a one-dimensional metal
embedded in a semi-conductor, and could potentially be used as a single-channel
quantum wire.Comment: 4 pgs. revte
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