English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Coplanar model states for applications of the coupled cluster method (CCM) toproblems in quantum magnetism are those in which all spins lie in a plane,whereas three-dimensional (3D) model states are, by contrast, non-coplanar onesin which all the spins do not lie in any single plane. Here we extend the CCMto non-coplanar / 3D model states and we present results for three cases: (a)the spin-half one-dimensional Ising ferromagnet in an applied transversemagnetic field (as an exactly solvable test model to use as a yardstick for theviability and accuracy of our new methodology); (b) the spin-halftriangular-lattice Heisenberg antiferromagnet in the presence of an externalmagnetic field; and (c) the spin-$S$ triangular-lattice {\it XXZ}antiferromagnet in the presence of an external magnetic field, for the cases$\frac{1}{2} \leq S \leq5 $. For 3D model states the sets of algebraic CCMequations for the ket- and bra-state correlation coefficients becomecomplex-valued, but ground-state expectation values of all physical observablesare manifestly real numbers, as required. Excellent correspondence is seen withthe results of other methods, where they exist, for these systems. CCM resultsdemonstrate explicitly that coplanar ordering is favoured over non-coplanarordering for the triangular-lattice spin-half Heisenberg antiferromagnet at allvalues of the applied external magnetic field, whereas for the anisotropic {\itXXZ} model non-coplanar ordering can be favoured in some regions of theparameter space. Specifically, we present a precise determination of theboundary (i.e., the critical value of the {\it XXZ} anisotropy parameter$\Delta$) between a 3D ground state and a coplanar ground state for the {\itXXZ} model for values for the external magnetic field near to saturation, forvalues of the spin quantum number $S \leq 5$.

Non-Coplanar Model States in Quantum Magnetism Applications of the High-Order Coupled Cluster Method