28 research outputs found
Topological Quantum Dimers Emerging from Kitaev Spin Liquid Bilayer: Anyon Condensation Transition
We present a bilayer spin model that illuminates the mechanism of topological
anyon condensation transition. Our model harbors two distinct topological
phases, Kitaev spin liquid bilayer state and resonating valence bond (RVB)
state connected by a continuous transition. We show that the transition occurs
by anyon condensation, and the hardcore dimer constraint of the RVB state plays
a role of the order parameter. This model study offers an intuitive picture for
anyon condensation transition, and is broadly applicable to generic
tri-coordinated lattices preserving the emergence of the RVB state from the
Kitaev bilayer.Comment: 6 pages, 4 figures + supplemental materia
Signatures of spin-triplet excitations in optical conductivity of valence bond solids
We show that the optical responses below the Mott gap can be used to probe
the spin-triplet excitations in valence bond solid (VBS) phases in Mott
insulators. The optical conductivity in this regime arises due to the
electronic polarization mechanism via virtual electron hopping processes. We
apply this mechanism to the Hubbard model with spin-orbit couplings and/or the
corresponding spin model with significant Dzyaloshinskii-Moriya (DM)
interactions, and compute the optical conductivity of VBS states on both ideal
and deformed Kagome lattices. In case of the deformed Kagome lattice, we study
the antiferromagnet, RbCuSnF with the pinwheel VBS state. In
case of the ideal Kagome lattice, we explore the optical conductivity
signatures of the spin-triplet excitations for three VBS states with (1) a
12-site unit cell, (2) a 36-site unit cell with six-fold rotation symmetry, and
(3) a 36-site unit cell with three-fold rotation symmetry, respectively. We
find that increasing the DM interactions generally leads to broad and smooth
features in the optical conductivity with interesting experimental
consequences. The optical conductivity reflects the features of the
spin-triplet excitations that can be measured in future experiments.Comment: Updated with the published version. 24 pages and 8 figure
Influence of Dzyaloshinskii-Moriya interactions on magnetic structure of a spin-1/2 deformed kagome lattice antiferromagnet
Motivated by the recent neutron scattering experiment on Rb2Cu3SnF12 [Nat.
Phys. 6, 865 (2010)], we investigate the effect of Dzyaloshinskii-Moriya
interactions in a theoretical model for the magnetic structure of this
material. Considering the valence bond solid ground state, which has a 12-site
unit cell, we develop the bond operator mean-field theory. It is shown that the
Dzyaloshinskii-Moriya interactions significantly modify the triplon dispersions
around the Gamma point and cause a shift of the spin gap (the minimum triplon
gap) position from the K to Gamma point in the first Brilloin zone. The spin
gap is also evaluated in exact diagonalization studies on a 24-site cluster. We
discuss a magnetic transition induced by the Dzyaloshinskii-Moriya interactions
in the bond operator framework. Moreover, the magnetization process under
external magnetic fields is studied within the exact diagonalization and strong
coupling expansion approaches. We find that the results of all above approaches
are consistent with the experimental findings.Comment: 14 pages, 10 figures; typos corrected, and acknowledgements and
references adde