4 research outputs found
Quantum manipulation of a two-level mechanical system
We consider a nonlinearly coupled electromechanical system, and develop a
quantitative theory for two-phonon cooling. In the presence of two-phonon
cooling, the mechanical Hilbert space is effectively reduced to its ground and
first excited states, thus forming a mechanical qubit. This allows for
performing quantum operations at the level of individual mechanical phonons and
preparing nonclassical mechanical states with negative Wigner functions. We
propose a scheme for performing arbitrary Bloch sphere rotations, and derive
the fidelity in the specific case of a -pulse. We characterise detrimental
processes that reduce the coherence in the system, and demonstrate that our
scheme can be implemented in state-of-the-art electromechanical devices.Comment: 6 pages main text + 7 pages supplemental material, 3 figure
Attractive trion-polariton nonlinearity due to Coulomb scattering
We theoretically investigate the nonlinearity of trion-polaritons in a
two-dimensional material that arises from Coulomb interaction between
quasiparticles. To evaluate the interaction constant, we solve a three-body
Wannier equation precisely by expanding trion wavefunctions into a Gaussian
basis. Using these wavefunctions, we calculate the trion-polariton interaction
energies for the exchange processes, resolving the outstanding question of
trion-trion scattering. We find that the nonlinearity is the result of the
competition between different scattering channels. Such a cancellation effect
is sensitive to wavefunction overlaps and depends on material parameters. Most
importantly, our result shows that the nonlinear interaction between
trion-polaritons is attractive, and is fivefold stronger than exciton-polariton
interaction. Our work thus describes the regime where trion-polaritons offer
the prospects for attractive fluids of light in monolayers of transition metal
dichalcogenides.Comment: 5 pages, 3 figures; the accompanying paper with all derivations will
be posted soo
Nonlinear interactions of dipolar excitons and polaritons in MoS2 bilayers
Nonlinear interactions between excitons strongly coupled to light are key for
accessing quantum many-body phenomena in polariton systems. Atomically-thin
two-dimensional semiconductors provide an attractive platform for strong
light-matter coupling owing to many controllable excitonic degrees of freedom.
Among these, the recently emerged exciton hybridization opens access to
unexplored excitonic species, with a promise of enhanced interactions. Here, we
employ hybridized interlayer excitons (hIX) in bilayer MoS2 to achieve highly
nonlinear excitonic and polaritonic effects. Such interlayer excitons possess
an out-of-plane electric dipole as well as an unusually large oscillator
strength allowing observation of dipolar polaritons(dipolaritons) in bilayers
in optical microcavities. Compared to excitons and polaritons in MoS2
monolayers, both hIX and dipolaritons exhibit about 8 times higher
nonlinearity, which is further strongly enhanced when hIX and intralayer
excitons, sharing the same valence band, are excited simultaneously. This gives
rise to a highly nonlinear regime which we describe theoretically by
introducing a concept of hole crowding. The presented insight into many-body
interactions provides new tools for accessing few-polariton quantum
correlations
Microscopic theory of exciton and trion polaritons in doped monolayers of transition metal dichalcogenides
We study a doped transition metal dichalcogenide (TMDC) monolayer in an optical microcavity. Using the microscopic theory, we simulate spectra of quasiparticles emerging due to the interaction of material excitations and a high-finesse optical mode, providing a comprehensive analysis of optical spectra as a function of Fermi energy and predicting several modes in the strong light-matter coupling regime. In addition to exciton-polaritons and trion-polaritons, we report polaritonic modes that become bright due to the interaction of excitons with free carriers. At large doping, we reveal strongly coupled modes corresponding to excited trions that hybridize with a cavity mode. We also demonstrate that the increase of carrier concentration can change the nature of the system's ground state from the dark to the bright one. Our results offer a unified description of polaritonic modes in a wide range of free electron densities