Abstract
AbstractBloch oscillations are a phenomenon well known from quantum mechanics where electrons in a lattice experience an oscillatory motion in the presence of an electric field gradient. Here, the authors report on Bloch oscillations of hybrid light−matter particles, called exciton‐polaritons (polaritons), being confined in an array of coupled microcavity waveguides. To this end, the waveguide widths and their mutual couplings are carefully designed such that a constant energy gradient is induced perpendicular to the direction of motion of the propagating polaritons. This technique allows us to directly observe and study Bloch oscillations in real‐ and momentum‐space. Furthermore, the experimental findings are supported by numerical simulations based on a modified Gross–Pitaevskii approach. This work provides an important transfer of basic concepts of quantum mechanics to integrated solid state devices, using quantum fluids of light.
Highlights
Bloch oscillations are a phenomenon well known from quantum mechanics understand electrical currents induced where electrons in a lattice experience an oscillatory motion in the presence of an electric field gradient
It was soon underconstant energy gradient is induced perpendicular to the direction of motion stood that those Bloch oscillations occur of the propagating polaritons
Already in the early days of quantum mechanics, the motion of line lattice under the action of a dc electric field, this single particles in a periodic potential under the action of a constant band picture had to be extended to take into account the coupling to other bands, an effect known as Zener tunneling.[2]
Summary
Propagating exciton-polaritons show one of the most spectacular phenomena of quantum fluids, namely superfluidity,[17,18] manifesting itself as the suppression of scattering from defects when the flow velocity is less than the speed of sound in the fluid. The required conditions and stability of Bloch oscillations have been theoretically estimated for a 1D lattice embedded into a semiconductor resonator operating in the strong light-matter coupling regime.[28,29] Here, we implement a 1D waveguide array for exciton-polaritons, supporting a significant gradient perpendicular to the direction of motion, unequivocally demonstrating polariton Bloch oscillations. We take advantage of the etch-and-overgrowth technique which allows for a large range and precise control of the coupling strength between two adjacent trapping potentials
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