733 research outputs found
Magnetization plateaus and sublattice ordering in easy axis Kagome lattice antiferromagnets
We study kagome lattice antiferromagnets where the effects of easy axis
single-ion anisotropy () dominates over the Heisenberg exchange . For , virtual quantum fluctuations help lift the extensive classical
degeneracy. We demonstrate the presence of a one-third magnetization plateau
for a broad range of magnetic fields along the
easy axis. The fully equilibriated system at low temperature on this plateau
develops an unusual {\em nematic} order that breaks sublattice rotation
symmetry but not translation symmetry--however, extremely slow dynamics
associated with this ordering is expected to lead to glassy freezing of the
system on intermediate time-scales.Comment: published versio
Extending Luttinger's theorem to Z(2) fractionalized phases of matter
Luttinger's theorem for Fermi liquids equates the volume enclosed by the
Fermi surface in momentum space to the electron filling, independent of the
strength and nature of interactions. Motivated by recent momentum balance
arguments that establish this result in a non-perturbative fashion [M.
Oshikawa, Phys. Rev. Lett. {\bf 84}, 3370 (2000)], we present extensions of
this momentum balance argument to exotic systems which exhibit quantum number
fractionalization focussing on fractionalized insulators, superfluids and
Fermi liquids. These lead to nontrivial relations between the particle filling
and some intrinsic property of these quantum phases, and hence may be regarded
as natural extensions of Luttinger's theorem. We find that there is an
important distinction between fractionalized states arising naturally from half
filling versus those arising from integer filling. We also note how these
results can be useful for identifying fractionalized states in numerical
experiments.Comment: 24 pages, 5 eps figure
Anomalous Zeeman response in coexisting phase of superconductivity and spin-density wave as a probe of extended -wave pairing structure in ferro-pnictide
In several members of the ferro-pnictides, spin density wave (SDW) order
coexists with superconductivity over a range of dopings. In this letter we
study the anomalous magnetic Zeeman response of this coexistence state and show
that it can be used to confirm the extended s-wave gap structure as well as
structure of superconducting (SC) gap in coexisting phase. On increasing the
field, a strongly anisotropic reduction of SC gap is found. The anisotropy is
directly connected to the gap structure of superconducting phase. The signature
of this effect in quasiparticle interference measured by STM, as well as heat
transport in magnetic field is discussed. For the compounds with the nodal SC
gap we show that the nodes are removed upon formation of SDW. Interestingly the
size of the generated gap in the originally nodal areas is anisotropic in the
position of the nodes over the Fermi surface in direct connection with the form
of SC pairing.Comment: 5 pages, 2 figure
Doping a spin-orbit Mott Insulator: Topological Superconductivity from the Kitaev-Heisenberg Model and possible application to (Na2/Li2)IrO3
We study the effects of doping a Mott insulator on the honeycomb lattice
where spins interact via direction dependent Kitaev couplings J_K, and weak
antiferromagnetic Heisenberg couplings J. This model is known to have a spin
liquid ground state and may potentially be realized in correlated insulators
with strong spin orbit coupling. The effect of hole doping is studied within a
t-J-J_K model, treated using the SU(2) slave boson formulation, which correctly
captures the parent spin liquid. We find superconductor ground states with spin
triplet pairing that spontaneously break time reversal symmetry. Interestingly,
the pairing is qualitatively different at low and high dopings, and undergoes a
first order transition with doping. At high dopings, it is smoothly connected
to a paired state of electrons propagating with the underlying free particle
dispersion. However, at low dopings the dispersion is strongly influenced by
the magnetic exchange, and is entirely different from the free particle band
structure. Here the superconductivity is fully gapped and topological,
analogous to spin polarized electrons with px+ipy pairing. These results may be
relevant to honeycomb lattice iridates such as A2IrO3 (A=Li or Na) on doping.Comment: 8 pages + 6 pages supplementary material; 5 figures, 3 tabl
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