Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First- and Second-Order Phase Transitions, Fulde-Ferrel Inhomogeneous
  State and Quantum Criticality in Ferromagnet/Superconductor Double Tunnel
  Junctions   First- and second-order phase transitions, Fulde-Ferrel (FF) inhomogeneous
superconducting (SC) state and quantum criticality in
ferromagnet/superconductor/ferromagnet double tunnel junctions are
investigated. For the antiparallel alignment of magnetizations, it is shown
that a first-order phase transition from the homogeneous BCS state to the
inhomogeneous FF state occurs at a certain bias voltage $V^{\ast}$; while the
transitions from the BCS state and the FF state to the normal state at $%
V_{c}$ are of the second-order. A phase diagram for the central superconductor
is presented. In addition, a quantum critical point (QCP), $% V_{QCP}$, is
identified. It is uncovered that near the QCP, the SC gap, the chemical
potential shift induced by the spin accumulation, and the difference of free
energies between the SC and normal states vanish as $% |V-V_{QCP}|^{z\nu}$ with
the quantum critical exponents $z\nu =1/2$, 1 and 2, respectively. The tunnel
conductance and magnetoresistance are also discussed.

34
The categories of this paper are: chem-ph
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an