224 research outputs found
Possibility of S=1 spin liquids with fermionic spinons on triangular lattices
In this paper we generalize the fermionic representation for spins to
arbitrary spins. Within a mean field theory we obtain several spin liquid
states for spin antiferromagnets on triangular lattices, including
gapless f-wave spin liquid and topologically nontrivial spin liquid.
After considering different competing orders, we construct a phase diagram for
the -- model. The application to recently discovered material
is discussed.Comment: 5 pages, 3 figure
Fermionic theory for quantum antiferromagnets with spin S > 1/2
The fermion representation for S = 1/2 spins is generalized to spins with
arbitrary magnitudes. The symmetry properties of the representation is analyzed
where we find that the particle-hole symmetry in the spinon Hilbert space of S
=1/2 fermion representation is absent for S > 1/2. As a result, different path
integral representations and mean field theories can be formulated for spin
models. In particular, we construct a Lagrangian with restored particle-hole
symmetry, and apply the corresponding mean field theory to one dimensional (1D)
S = 1 and S = 3/2 antiferromagnetic Heisenberg models, with results that agree
with Haldane's conjecture. For a S = 1 open chain, we show that Majorana
fermion edge states exist in our mean field theory. The generalization to spins
with arbitrary magnitude S is discussed. Our approach can be applied to higher
dimensional spin systems. As an example, we study the geometrically frustrated
S = 1 AFM on triangular lattice. Two spin liquids with different pairing
symmetries are discussed: the gapped px + ipy-wave spin liquid and the gapless
f-wave spin liquid. We compare our mean field result with the experiment on
NiGa2S4, which remains disordered at low temperature and was proposed to be in
a spin liquid state. Our fermionic mean field theory provide a framework to
study S > 1/2 spin liquids with fermionic spinon excitations.Comment: 16 pages, 4 figure
The relationship between blogs and newspapers in Singapore: An intermedia agenda-setting study
Master'sMASTER OF ART
Superfluid Density of a Spin-orbit Coupled Bose Gas
We discuss the superfluid properties of a Bose-Einstein condensed gas with
spin-orbit coupling, recently realized in experiments. We find a finite normal
fluid density at zero temperature which turns out to be a function of
the Raman coupling. In particular, the entire fluid becomes normal at the
transition point from the zero momentum to the plane wave phase, even though
the condensate fraction remains finite. We emphasize the crucial role played by
the gapped branch of the elementary excitations and discuss its contributions
to various sum rules. Finally, we prove that an independent definition of
superfluid density , using the phase twist method, satisfies the
equality , the total density, despite the breaking of
Galilean invariance
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