Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Competing Orders and Ultrafast Energy Transfer at the Quantum Limit in a
  Nb$_3$Sn Superconductor Probed by Terahertz Electrodynamics   We report the low-energy electrodynamics of a moderately clean A15
superconductor (SC) following ultrafast excitation to understand and manipulate
terahertz (THz) quasi--particle (QP) transport by tuning pump photoexcitation
of from competing orders. Using 35-fs optical pulses, we observe a non-thermal
enhancement in the low frequency conductivity, opposite to that observed for
THz pump, which persists up to an additional critical temperature, above the SC
one, from an electronic order in the Martensitic normal state. In the SC state,
the fluence dependence of pair breaking kinetics together with an analytic
model provides evidence for a `one photon-to-one pair' non-resonant energy
transfer during the laser pulse. Such initial transfer of photon energy
$\hbar\omega$ to QPs at the {\em quantum} limit, set by
$2\Delta_{SC}/\hbar\omega$=0.33$\%$, is more than one order of magnitude
smaller than in previously studied BCS SCs, which we attribute to strong
electron--phonon coupling and possible influence of phonon condensation in A15
SCs.

20
The categories of this paper are: acc-phys
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th