194 research outputs found
Magnetic field induced topological nodal-lines in triplet excitations of frustrated antiferromagnet CaVO
Magnetic field induced multiple non-Dirac nodal-lines are found to emerge in
the triplet dispersion bands of a frustrated spin-1/2 antiferromagnetic model
on the CaVO lattice. Plaquette and bond operator formalisms have been employed
to obtain the triplet plaquette and bond excitations for two different
parameter regimes in the presence of nearest and next-nearest-neighbor
Heisenberg interactions based on the plaquette-resonating-valence-bond and
dimerized ground states, respectively. In the absence of magnetic field a pair
of six-fold degenerate nodal-loops with distinct topological feature is noted
in the plaquette excitations. They are found to split into three pairs of
two-fold degenerate nodal-loops in the presence of magnetic field. In the other
parameter regime, system hosts two-fold degenerate multiple nodal-lines with a
variety of shapes in the triplon dispersion bands in the presence of magnetic
field. Ground state energy and spin gap have been determined additionally for
the two regimes. Those nodal-lines are expected to be detectable in neutron
scattering experiment on the frustrated antiferromagnet, CaVO.Comment: 15 pages, 17 figure
Thermally stable multipartite entanglements in the frustrated Heisenberg hexagon
Thermally stable quantum states with multipartite entanglements led by
frustration are found in the antiferromagnetic spin-1/2 Heisenberg hexagon. The
model has been solved exactly to obtain all analytic expressions of eigenvalues
and eigenfunctions. Detection and characterizations for various types of
entanglements have been carried out in terms of concurrence and entanglement
witnesses based on several thermodynamic observables. Variations of
entanglement properties with respect to temperature and frustration are
discussed. Even though the frustration opposes the bipartite entanglement, it
favors the multipartite entanglement. Entangled states exhibit robustness
against the thermal effects in the presence of frustration and they are found
to survive at any temperature.Comment: 25 pages, double space, single column, 5 figure
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