7 research outputs found
Non-Local Exciton-Photon Interactions in Hybrid High-Q Beam Nanocavities with Encapsulated MoS2 Monolayers
Atomically thin semiconductors can be readily integrated into a wide range of
nanophotonic architectures for applications in quantum photonics and novel
optoelectronic devices. We report the observation of non-local interactions of
\textit{free} trions in pristine hBN/MoS/hBN heterostructures coupled to
single mode (Q ) quasi 0D nanocavities. The high excitonic and photonic
quality of the interaction system stem from our integrated nanofabrication
approach simultaneously with the hBN encapsulation and the maximized local
cavity field amplitude within the MoS monolayer. We observe a non-monotonic
temperature dependence of the cavity-trion interaction strength, consistent
with the non-local light-matter interactions in which the extent of the
center-of-mass wavefunction is comparable to the cavity mode volume in space.
Our approach can be generalized to other optically active 2D materials, opening
the way towards harnessing novel light-matter interaction regimes for
applications in quantum photonics
Exploring the phonon-assisted excitation mechanism of luminescent centres in hexagonal boron nitride by photoluminescence excitation spectroscopy
The two-dimensional material hexagonal boron nitride (hBN) hosts
single-photon emitters active at room temperature. However, the microscopic
origin of these emitters, as well as the mechanism through which they are
excited, remain elusive. We address these issues by combining \emph{ab initio}
calculations with low-temperature photoluminescence excitation spectroscopy. By
studying 26 defect transitions, we find excellent qualitative agreement of
experiments with the emission and absorption line shapes of the carbon trimers
and , while enabling us to exclude 24 defect
transitions for one luminescent centre. Furthermore, we show an enhanced
zero-phonon line intensity at two-phonon detuning. This unambiguously
demonstrates that luminescent centers in hBN, and by inference single-photon
emitters, are excited through a phonon-assisted mechanism. To the best of our
knowledge, this study provides the most comprehensive insight into the
excitation mechanism and the microscopic origin of luminescent centers in hBN
Spectral X-ray dark-field signal characterization from dual-energy projection phase-stepping data with a Talbot-Lau interferometer
Abstract Material-selective analysis of spectral X-ray imaging data requires prior knowledge of the energy dependence of the observed signal. Contrary to conventional X-ray imaging, where the material-specific attenuation coefficient is usually precisely known, the linear diffusion coefficient of the X-ray dark-field contrast does not only depend on the material and its microstructure, but also on the setup geometry and is difficult to access. Here, we present an optimization approach to retrieve the energy dependence of the X-ray dark-field signal quantitatively on the example of closed-cell foams from projection data without the need for additional hardware to a standard grating-based X-ray dark-field imaging setup. A model for the visibility is used to determine the linear diffusion coefficient with a least-squares optimization. The comparison of the results to spectrometer measurements of the linear diffusion coefficient suggests the proposed method to provide a good estimate for the energydependent dark-field signal
Low-temperature spectroscopy of single-photon emitters in irradiation-engineered hexagonal boron nitride
Photoluminescence excitation spectroscopy of luminescent centres in hexagonal boron nitride
Combining experiments on luminescent centres in hexagonal boron nitride with the polaron model and ab initio methods towards the identification of their microscopic origin
The two-dimensional material hexagonal boron nitride (hBN) hosts luminescent centres with emission energies of ∼2 eV which exhibit pronounced phonon sidebands. We investigate the microscopic origin of these luminescent centres by combining ab initio calculations with non-perturbative open quantum system theory to study the emission and absorption properties of 26 defect transitions. Comparing the calculated line shapes with experiments we narrow down the microscopic origin to three carbon-based defects: C2CB, C2CN, and VNCB. The theoretical method developed enables us to calculate so-called photoluminescence excitation (PLE) maps, which show excellent agreement with our experiments. The latter resolves higher-order phonon transitions, thereby confirming both the vibronic structure of the optical transition and the phonon-assisted excitation mechanism with a phonon energy ∼170 meV. We believe that the presented experiments and polaron-based method accurately describe luminescent centres in hBN and will help to identify their microscopic origin