22 research outputs found
Ultrastrong coupling between a cavity resonator and the cyclotron transition of a 2D electron gas in the case of integer filling factor
We investigate theoretically the coupling between a cavity resonator and the
cyclotron transition of a two dimensional electron gas under an applied
perpendicular magnetic field. We derive and diagonalize an effective quantum
Hamiltonian describing the magnetopolariton excitations of the two dimensional
electron gas for the case of integer filling factors. The limits of validity of
the present approach are critically discussed. The dimensionless vacuum Rabi
frequency (i.e., normalized to the cyclotron frequency
) is shown to scale as , where
is the fine structure constant, is the number of quantum wells and
is the filling factor in each well. We show that with realistic
parameters of a high-mobility semiconductor two dimensional electron gas, the
dimensionless coupling can be much larger than 1 in the
case of , the latter condition being typically realized for
cyclotron transitions in the microwave range. Implications of such ultrastrong
coupling regime are discussed
Cavity-assisted mesoscopic transport of fermions: Coherent and dissipative dynamics
We study the interplay between charge transport and light-matter interactions
in a confined geometry, by considering an open, mesoscopic chain of two-orbital
systems resonantly coupled to a single bosonic mode close to its vacuum state.
We introduce and benchmark different methods based on self-consistent solutions
of non-equilibrium Green's functions and numerical simulations of the quantum
master equation, and derive both analytical and numerical results. It is shown
that in the dissipative regime where the cavity photon decay rate is the
largest parameter, the light-matter coupling is responsible for a steady-state
current enhancement scaling with the cooperativity parameter. We further
identify different regimes of interest depending on the ratio between the
cavity decay rate and the electronic bandwidth. Considering the situation where
the lower band has a vanishing bandwidth, we show that for a high-finesse
cavity, the properties of the resonant Bloch state in the upper band are
transfered to the lower one, giving rise to a delocalized state along the
chain. Conversely, in the dissipative regime with low cavity quality factors,
we find that the current enhancement is due to a collective decay of
populations from the upper to the lower band.Comment: 52 pages, 11 figure
Ensemble-induced strong light-matter coupling of a single quantum emitter
We discuss a technique to strongly couple a single target quantum emitter to
a cavity mode, which is enabled by virtual excitations of a nearby mesoscopic
ensemble of emitters. A collective coupling of the latter to both the cavity
and the target emitter induces strong photon non-linearities in addition to
polariton formation, in contrast to common schemes for ensemble strong
coupling. We demonstrate that strong coupling at the level of a single emitter
can be engineered via coherent and dissipative dipolar interactions with the
ensemble, and provide realistic parameters for a possible implementation with
SiV defects in diamond. Our scheme can find applications, amongst others,
in quantum information processing or in the field of cavity-assisted quantum
chemistry.Comment: 13 pages, 6 figures; substantially revised manuscript; see
arXiv:1912.12703 for mathematical derivation
Anomalous diffusion in the Long-Range Haken-Strobl-Reineker model
We analyze the propagation of excitons in a -dimensional lattice with
power-law hopping in the presence of dephasing, described
by a generalized Haken-Strobl-Reineker model. We show that in the strong
dephasing (quantum Zeno) regime the dynamics is described by a classical master
equation for an exclusion process with long jumps. In this limit, we
analytically compute the spatial distribution, whose shape changes at a
critical value of the decay exponent . The exciton
always diffuses anomalously: a superdiffusive motion is associated to a L\'evy
stable distribution with long-range algebraic tails for , while for the distribution corresponds to a
surprising mixed Gaussian profile with long-range algebraic tails, leading to
the coexistence of short-range diffusion and long-range L\'evy-flights. In the
many-exciton case, we demonstrate that, starting from a domain-wall exciton
profile, algebraic tails appear in the distributions for any , which
affects thermalization: the longer the hopping range, the faster equilibrium is
reached. Our results are directly relevant to experiments with cold trapped
ions, Rydberg atoms and supramolecular dye aggregates. They provide a way to
realize an exclusion process with long jumps experimentally.Comment: 5 pages, 2 figure
Non-Invasive Time-Lapsed Monitoring and Quantification of Engineered Bone-Like Tissue
The formation of bone-like tissue from human mesenchymal stem cells (hMSC) cultured in osteogenic medium on silk fibroin scaffolds was monitored and quantified over 44days in culture using non-invasive time-lapsed micro-computed tomography (μCT). Each construct was imaged nine times insitu. From μCT imaging, detailed morphometrical data on bone volume density, surface-to-volume ratio, trabecular thickness, trabecular spacing, and the structure model index and tissue mineral density were obtained. μCT irradiation did not impact the osteogenic performance of hMSCs based on DNA content, alkaline phosphatase activity, and calcium deposition when compared to non-exposed control samples. Bone-like tissue formation initiated at day 10 of the culture with the deposition of small mineralized clusters. Tissue mineral density increased linearly over time. The surface-to-volume ratio of the bone-like tissues converged asymptotically to 26mm−1. Although in vitro formation of bone-like tissue started from clusters, the overall bone volume was not predictable from the time, number, and size of initially formed bone-like clusters. Based on microstructural analysis, the morphometry of the tissue-engineered constructs was found to be in the range of human trabecular bone. In future studies, non-invasive, time-lapsed monitoring may enable researchers to culture tissues in vitro, right until the development of a desired morphology is accomplished. Our data demonstrate the feasibility of qualitatively and quantitatively detailing the spatial and temporal mineralization of bone-like tissue formation in tissue engineerin
Ultrastrong coupling of the cyclotron transition of a two-dimensional electron gas to a THz metamaterial
Artificial cavity photon resonators with ultrastrong light-matter
interactions are attracting interest both in semiconductor and superconducting
systems, due to the possibility of manipulating the cavity quantum
electrodynamic ground state with controllable physical properties. We report
here experiments showing ultrastrong light-matter coupling in a terahertz
metamaterial where the cyclotron transition of a high mobility two-dimensional
electron gas is coupled to the photonic modes of an array of electronic
split-ring resonators.
We observe a normalized coupling ratio between
the vacuum Rabi frequency and the cyclotron frequency . Our
system appears to be scalable in frequency and could be brought to the
microwave spectral range with the potential of strongly controlling the
magnetotransport properties of a high-mobility 2DEG
Ultrastrong photon-photon coupling
Correlations between photons are a key feature of nonclassical states of
light. Recent studies suggest that the ground state of a cavity quantum
electrodynamics system can have light-matter correlations in the form of a
squeezed vacuum state in thermal equilibrium when the matter ultrastrongly
couples with cavity photons. This raises a question whether different photonic
modes can also be correlated in the ground state via ultrastrong light-matter
coupling. Here we demonstrate ultrastrong coupling between photonic modes of a
multi-mode three-dimensional terahertz photonic-crystal cavity that is mediated
by their simultaneous ultrastrong coupling with the cyclotron resonance of a
two-dimensional electron gas in GaAs. Terahertz spectroscopy measurements of
Landau polaritons showed excellent agreement with our calculations based on a
microscopic quantum model. Despite the lack of nonlinearity in the matter
system, the model shows significant correlations between the photonic modes in
the ground state of the system, which can be controlled by changing the matter
and photon frequencies and the spatial overlap of their mode profiles. We
propose a detuning-independent figure of merit to quantify all possible
couplings in multi-mode systems. These findings pave the way for creating
multi-mode nonclassical states and exploring the many-body regime of quantum
optics with vacuum fields.Comment: 32 pages, 12 figure