488 research outputs found
d-Wave Pairing in an Ensemble of Spin Polaron Quasiparticles in the Spin-Fermion Model of the Electronic Structure of the CuO2 Plane
It is demonstrated for the first time that the strong coupling between spin
moments of copper ions and oxygen holes, which arises upon hybridazation mixing
of two hole subsystems in the Emery model, not only affects the formation of
spin polaron quasiparticles but also ensures effective attraction between them
via the exchange interaction. This results in the Cooper instability with
d-wave pairing in a 2D ensemble of spin polaron quasiparticles. The T-x-phase
diagram obtained using this approach agrees well with the available
experimental data
Thermodynamics of symmetric spin--orbital model: One- and two-dimensional cases
The specific heat and susceptibilities for the two- and one-dimensional
spin--orbital models are calculated in the framework of a spherically symmetric
self-consistent approach at different temperatures and relations between the
parameters of the system. It is shown that even in the absence of the
long-range spin and orbital order, the system exhibits the features in the
behavior of thermodynamic characteristics, which are typical of those
manifesting themselves at phase transitions. Such features are attributed to
the quantum entanglement of the coupled spin and orbital degrees of freedom.Comment: 7 pages, 9 figures, submitted to JETP Letter
Continuous transformation between ferro and antiferro circular structures in frustrated Heisenberg model
Frustrated magnetic compounds, in particular low-dimensional, are topical
research due to persistent uncover of novel nontrivial quantum states and
potential applications. The problem of this field is that many important
results are scattered over the localized parameter ranges, while areas in
between still contain hidden interesting effects. We consider
Heisenberg model on the square lattice and use the spherically symmetric
self-consistent approach for spin-spin Green's functions in "quasielastic"
approximation. We have found a new local order in spin liquids:
antiferromagnetic isotropical helices. On the structure factor we see circular
concentric dispersionless structures, while on any radial direction the
excitation spectrum has "roton" minima. That implies nontrivial magnetic
excitations and consequences in magnetic susceptibility and thermodynamics. On
the exchange parameters globe we discover a crossover between
antiferromagnetic-like local order and ferromagnetic-like; we find stripe-like
order in the middle. In fact, our "quasielastic" approach allows investigation
of the whole globe.Comment: 9 pages, 12 figure
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