Physics A fascinating property of the quantum world is that particles come equipped with a dual, wavelike nature, which becomes apparent at low temperatures and high densities. For a certain type of particle, bosons, this results in the formation of a giant wave, a Bose-Einstein condensate (BEC). BECs have been realized in laser-trapped ultracold gases of alkali elements, but bosons that exist elsewhere in nature are also expected to condense. An exciton is a composite boson consisting of an electron and a hole (a missing electron) in a semiconductor. High et al. take a page out of the atomic physicists' book and demonstrate the condensation of excitons in a trap. A spatially varying electric field traps the excitons' dipole moments, which are nonzero because of the spatial separation of electrons and holes in a GaAs/AlGaAs coupled quantum well (such so-called indirect excitons also have the advantage of a long lifetime necessary for cooling). When the temperature is lowered below ~2 K, the excitons collect at the trap center, and the entire trap volume becomes coherent, signifying the onset of a BEC. The realization of a BEC in a trapped semiconductor system is expected to enable explorations complementary to those possible with ultracold atomic gases. Nano Lett. 12 , 10.1021/nl300983n (2012).Physics A fascinating property of the quantum world is that particles come equipped with a dual, wavelike nature, which becomes apparent at low temperatures and high densities. For a certain type of particle, bosons, this results in the formation of a giant wave, a Bose-Einstein condensate (BEC). BECs have been realized in laser-trapped ultracold gases of alkali elements, but bosons that exist elsewhere in nature are also expected to condense. An exciton is a composite boson consisting of an electron and a hole (a missing electron) in a semiconductor. High et al. take a page out of the atomic physicists' book and demonstrate the condensation of excitons in a trap. A spatially varying electric field traps the excitons' dipole moments, which are nonzero because of the spatial separation of electrons and holes in a GaAs/AlGaAs coupled quantum well (such so-called indirect excitons also have the advantage of a long lifetime necessary for cooling). When the temperature is lowered below ~2 K, the excitons collect at the trap center, and the entire trap volume becomes coherent, signifying the onset of a BEC. The realization of a BEC in a trapped semiconductor system is expected to enable explorations complementary to those possible with ultracold atomic gases. Nano Lett. 12 , 10.1021/nl300983n (2012).

ScienceMay 17, 20120 citations

Bose-Einstein Condensation of Excitons

Claude Benoit à la Guillaume, Erio Tosatti

Europhysics newsJan 1, 19740 citations

Superradiance fingerprints of moiré exciton-biexciton condensates: path-entangled biphoton vs. supercurrent-enabled one-photon channel

Haochen Wang, Shengxian Li, Hongyu Lu +2 more

Hybrid moiré excitons form a dense array of electrically tunable single-photon emitters, entailing cooperative optical responses with intriguing consequences. With the strong dipole-dipole interaction, they also realize Bose-Hubbard quantum simulators of emergent correlated matter such as Bose-Einstein condensates (BEC). Here we reveal the characteristic cooperative radiation from condensates of hybrid moiré excitons in twisted MoTe $_2$ bilayers. In each individual moiré trap, the layer hybridization selection rule dictates that the ground-state exciton is a quantum emitter of orbital-angular-momentum photons, with an exceptionally long radiative lifetime. Ground-state emission becomes pronounced only upon forming condensates, where inter-sublattice dipole attraction and intra-sublattice repulsion together lead to the coexistence of exciton and biexciton BEC with comparable weights. The biexciton (molecular-type) BEC decays through superradiance of path-entangled biphotons, whereas the exciton (atomic-type) BEC is dark at rest and becomes superradiant when it carries a supercurrent. Our findings not only uncover a novel source of entangled light but also establish unique fingerprints for exploring the cold chemistry of atomic-molecular condensates with moiré excitons.Hybrid moiré excitons form a dense array of electrically tunable single-photon emitters, entailing cooperative optical responses with intriguing consequences. With the strong dipole-dipole interaction, they also realize Bose-Hubbard quantum simulators of emergent correlated matter such as Bose-Einstein condensates (BEC). Here we reveal the characteristic cooperative radiation from condensates of hybrid moiré excitons in twisted MoTe$_2$ bilayers. In each individual moiré trap, the layer hybridization selection rule dictates that the ground-state exciton is a quantum emitter of orbital-angular-momentum photons, with an exceptionally long radiative lifetime. Ground-state emission becomes pronounced only upon forming condensates, where inter-sublattice dipole attraction and intra-sublattice repulsion together lead to the coexistence of exciton and biexciton BEC with comparable weights. The biexciton (molecular-type) BEC decays through superradiance of path-entangled biphotons, whereas the exciton (atomic-type) BEC is dark at rest and becomes superradiant when it carries a supercurrent. Our findings not only uncover a novel source of entangled light but also establish unique fingerprints for exploring the cold chemistry of atomic-molecular condensates with moiré excitons.

cond-mat.mes-hallCross-listedarXiv:2611.01515Nov 3, 2026

Tunable Bose-Einstein condensation and rotonlike excitation spectra with dipolar exciton-polaritons in crossed fields

Timofey V. Maximov, I. L. Kurbakov, Nina S. Voronova +1 more

We develop the many-body theory of dipolar exciton-polaritons in an optical microcavity in crossed out-of-plane electric and in-plane magnetic fields. Even for relatively weak fields, we reveal the existence of two minima in the bare lower-polariton dispersion, which give rise to the tunable transition between the polariton Bose-Einstein condensate and that of excitons, produced by the competition between these minima. We predict that such dipolar condensate exhibits a roton-maxon character of the excitation spectrum, never before observed for polaritons. We show that upon the transition between the two condensation regimes, the weak correlations in the polariton gas give way to the intermediate interparticle correlations characteristic for excitons, and that the transition is accompanied by a sharp quenching of photoluminescence as the lifetime is increased by several orders of magnitude. While in the polariton regime, the luminescence peak corresponding to the condensate is shifted to a nonzero angle. The angular dependence of the two-photon decay time in the Hanbury Brown and Twiss experiment is calculated and used as a tool to evidence the formation of the macroscopically coherent state. Our proposal opens opportunities towards manipulating the superfluid properties and extended-range dipole-dipole correlations of exciton-polariton condensates.We develop the many-body theory of dipolar exciton-polaritons in an optical microcavity in crossed out-of-plane electric and in-plane magnetic fields. Even for relatively weak fields, we reveal the existence of two minima in the bare lower-polariton dispersion, which give rise to the tunable transition between the polariton Bose-Einstein condensate and that of excitons, produced by the competition between these minima. We predict that such dipolar condensate exhibits a roton-maxon character of the excitation spectrum, never before observed for polaritons. We show that upon the transition between the two condensation regimes, the weak correlations in the polariton gas give way to the intermediate interparticle correlations characteristic for excitons, and that the transition is accompanied by a sharp quenching of photoluminescence as the lifetime is increased by several orders of magnitude. While in the polariton regime, the luminescence peak corresponding to the condensate is shifted to a nonzero angle. The angular dependence of the two-photon decay time in the Hanbury Brown and Twiss experiment is calculated and used as a tool to evidence the formation of the macroscopically coherent state. Our proposal opens opportunities towards manipulating the superfluid properties and extended-range dipole-dipole correlations of exciton-polariton condensates.

arXiv:2306.02202Physical review. B./Physical review. BNov 13, 20233 citations

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bilayers. In each individual moiré trap, the layer hybridization selection rule dictates that the ground-state exciton is a quantum emitter of orbital-angular-momentum photons, with an exceptionally long radiative lifetime. Ground-state emission becomes pronounced only upon forming condensates, where inter-sublattice dipole attraction and intra-sublattice repulsion together lead to the coexistence of exciton and biexciton BEC with comparable weights. The biexciton (molecular-type) BEC decays through superradiance of path-entangled biphotons, whereas the exciton (atomic-type) BEC is dark at rest and becomes superradiant when it carries a supercurrent. Our findings not only uncover a novel source of entangled light but also establish unique fingerprints for exploring the cold chemistry of atomic-molecular condensates with moiré excitons.