Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Frustrated quantum Heisenberg antiferromagnets at high magnetic fields:
  Beyond the flat-band scenario   We consider the spin-1/2 antiferromagnetic Heisenberg model on three
frustrated lattices (the diamond chain, the dimer-plaquette chain and the
two-dimensional square-kagome lattice) with almost dispersionless lowest magnon
band. Eliminating high-energy degrees of freedom at high magnetic fields, we
construct low-energy effective Hamiltonians which are much simpler than the
initial ones. These effective Hamiltonians allow a more extended analytical and
numerical analysis. In addition to the standard strong-coupling perturbation
theory we also use a localized-magnon based approach leading to a substantial
improvement of the strong-coupling approximation. We perform extensive exact
diagonalization calculations to check the quality of different effective
Hamiltonians by comparison with the initial models. Based on the
effective-model description we examine the low-temperature properties of the
considered frustrated quantum Heisenberg antiferromagnets in the high-field
regime. We also apply our approach to explore thermodynamic properties for a
generalized diamond spin chain model suitable to describe azurite at high
magnetic fields. Interesting features of these highly frustrated spin models
consist in a steep increase of the entropy at very small temperatures and a
characteristic extra low-temperature peak in the specific heat. The most
prominent effect is the existence of a magnetic-field driven
Berezinskii-Kosterlitz-Thouless phase transition occurring in the
two-dimensional model.

10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
19
The categories of this paper are: eess
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph
24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
11
The categories of this paper are: hep-lat
34
The categories of this paper are: chem-ph