Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Superconductivity, metastability and magnetic field induced phase
  separation in the atomic limit of the Penson-Kolb-Hubbard model   We present the analysis of paramagnetic effects of magnetic field ($B$)
(Zeeman term) in the zero-bandwidth limit of the extended Hubbard model for
arbitrary chemical potential $\mu$ and electron density $n$. The effective
Hamiltonian considered consists of the on-site interaction $U$ and the
intersite charge exchange term $I$, determining the hopping of electron pairs
between nearest-neighbour sites. The model has been analyzed within the
variational approach, which treats the on-site interaction term exactly and the
intersite interactions within the mean-field approximation (rigorous in the
limit of infinite dimensions $d\rightarrow+\infty$). In this report we focus on
metastable phases as well as phase separated (PS) states involving
superconducting (SS) and nonordered (NO) phases and determine their ranges of
occurrence for $U/I_0=1.05$ ($I_0=zI$) in the presence of magnetic field
$B\neq0$. Our investigations of the general case for arbitrary $U/I_0$ show
that, depending on the values of interaction parameters (for fixed $n$), the PS
state can occur in higher fields than the homogeneous SS phase (field-induced
PS). Moreover, a first-order SS-NO transition occurs between metastable phases
and these metastable phases can exist inside the regions of the PS state
stability. Such behaviour is associated with the presence of tricritical line
on the phase diagrams of the system.

31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
15
The categories of this paper are: nucl-ex
29
The categories of this paper are: funct-an
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
16
The categories of this paper are: stat
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
32
The categories of this paper are: atom-ph