Here, we explore LBS to uncover the Pancharatnam–Berry phase in a condensate of IXs. This variability gives the opportunity to measure correlations between coherence and polarization. Different LBS offer IX sources of different strength and spatial extension furthermore, these parameters can be controlled by optical excitation and voltage 21. An LBS is a stable, well defined, and tunable source of cold IXs 21, thus an ideal system for studying coherence and polarization phenomena. These rings form on the boundaries of electron-rich and hole-rich regions created by current through the structure and optical excitation, respectively see ref. The large coherence length observed in an IX condensate, reaching ~10 μm, indicates coherent IX transport with suppressed scattering 7, in agreement with theory 20.Ī cold IX gas is realized in the regions of the external ring and localized bright spot (LBS) rings in the IX emission 7, 8. IX condensation is detected by measurement of IX spontaneous coherence with a coherence length much larger than in a classical gas 7. Due to their long lifetimes IXs can cool below the temperature of quantum degeneracy and form a condensate in momentum ( k) space 7. IXs are realized in coupled quantum well (CQW) structures. This connection of the Pancharatnam–Berry phase to polarization makes it an intrinsic phenomenon for polarization textures.Īn IX is a bound pair of an electron and a hole confined in spatially separated layers. The Pancharatnam–Berry phase appears when the polarization state of light changes 1. Recent studies led to the discovery of polarization textures in light emission of indirect excitons (IXs) 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 and exciton–polaritons 17, 18, 19. This makes excitons a unique interface between matter and light and a unique system for exploring the Pancharatnam–Berry phase for matter waves by light interference experiments. Excitons are matter waves that directly transform to photons inheriting their coherence and polarization. For light, the Pancharatnam–Berry phase is measured in laser interferometers 3, 4 and exploited in optical elements 5, 6. ![]() The Pancharatnam–Berry phase was discovered by Pancharatnam in studies of polarized light 1 and introduced by Berry as a topological phase for matter wave functions 2.
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