Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A ferroelectric quantum phase transition inside the superconducting dome
  of Sr$_{1-x}$Ca$_{x}$TiO$_{3-\delta}$   SrTiO$_{3}$, a quantum paraelectric, becomes a metal with a superconducting
instability after removal of an extremely small number of oxygen atoms. It
turns into a ferroelectric upon substitution of a tiny fraction of strontium
atoms with calcium. The two orders may be accidental neighbors or intimately
connected, as in the picture of quantum critical ferroelectricity. Here, we
show that in Sr$_{1-x}$Ca$_{x}$TiO$_{3-\delta}$ ($0.002<x<0.009$,
$\delta<0.001$) the ferroelectric order coexists with dilute metallicity and
its superconducting instability in a finite window of doping. At a critical
carrier density, which scales with the Ca content, a quantum phase transition
destroys the ferroelectric order. We detect an upturn in the normal-state
scattering and a significant modification of the superconducting dome in the
vicinity of this quantum phase transition. The enhancement of the
superconducting transition temperature with calcium substitution documents the
role played by ferroelectric vicinity in the precocious emergence of
superconductivity in this system, restricting possible theoretical scenarios
for pairing.

14
The categories of this paper are: math-ph
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
9
The categories of this paper are: nlin
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
15
The categories of this paper are: nucl-ex
37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
10
The categories of this paper are: q-bio