183 research outputs found
Numerical Study of Carrier Multiplication Pathways in Nanocrystalline and Bulk Form of PbSe
Employing the interband exciton scattering model, we have performed a
numerical study of the direct photogeneration and population relaxation
processes contributing to carrier multiplication (CM) in nanocrystalline and
bulk PbSe. We argue that in both cases the impact ionization is the main
mechanisms of CM. This explains weak contribution of the direct photogeneration
to the total quantum efficiency (QE). Investigated size scaling of QE in NCs
and comparison to the bulk limit provide microscopic insight in the
experimentally observed trends.Comment: 4 pages, 3 figures (revised version) Accepted for publication in
Physical Review Letter
Degenerate parametric down-conversion facilitated by exciton-plasmon polariton states in nonlinear plasmonic cavity
We study the effect of degenerate parametric down-conversion (DPDC) in an
ensemble of two-level quantum emitters (QEs) coupled via near-field
interactions to a single surface plasmon (SP) mode of a nonlinear plasmonic
cavity. For this purpose, we develop a quantum driven-dissipative model
capturing non-equilibrium dynamics of the system in which incoherently pumped
QEs have transition frequency tuned near the second-harmonic response of the
SPs. Considering the strong coupling regime, i.e., the SP-QE interaction rate
exceeds system dissipation rates, we find a critical SP-QE coupling attributed
to the phase transition between normal and lasing steady states. Examining
fluctuations above the system's steady states, we predict new elementary
excitations, namely, the exciton-plasmon polaritons formed by the two-SP quanta
and single-exciton states of QEs. The contribution of two-SP quanta results in
the linear scaling of the SP-QE interaction rate with the number of QEs, , as opposed to the -scaling known for the Dicke and
Tavis-Cummings models. We further examine how SP-QE interaction scaling affects
the polariton dispersions and power spectra in the vicinity of the critical
coupling. For this purpose, we compare the calculation results assuming a
finite ensemble of QEs and the model thermodynamic limit. The calculated power
spectra predict an interplay of coherent photon emission by QEs near the
second-harmonic frequency and correlated photon-pair emission at the
fundamental frequency by the SPs (i.e., the photonic DPDC effect).Comment: 8 pages, 3 figure
Probing dynamical symmetry breaking using quantum-entangled photons
We present an input/output analysis of photon-correlation experiments whereby
a quantum mechanically entangled bi-photon state interacts with a material
sample placed in one arm of a Hong-Ou-Mandel (HOM) apparatus. We show that the
output signal contains detailed information about subsequent entanglement with
the microscopic quantum states in the sample. In particular, we apply the
method to an ensemble of emitters interacting with a common photon mode within
the open-system Dicke Model. Our results indicate considerable dynamical
information concerning spontaneous symmetry breaking can be revealed with such
an experimental system
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