Condensation of excitons in Cu<sub>2</sub>O at ultracold temperatures: experiment and theory

Stolz, H.; Schwartz, Rico; Kieseling, F.; Som, Sunipa; Kaupsch, Maria; Sobkowiak, S.; Semkat, D.; Naka, N.; Koch, Thomas; Fehske, Holger

doi:10.1088/1367-2630/14/10/105007

Cited by 41 publications

(58 citation statements)

References 73 publications

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“…One can immediately see that the low mass of Ps allows for much higher critical temperatures than any other atom (although some condensed matter systems such as excitons [660] or exciton-polaritons [661] may have critical temperatures similar to or higher than Ps at equivalent densities). A Ps density of 10 17 cm −3 would start to BoseCondense at a temperature of ≈3 K. Note, however, that T C is the temperature at which condensation starts to happen: the condensate occupancy is given by…”

Section: Bose-einstein Condensationmentioning

confidence: 99%

Experimental progress in positronium laser physics

2018

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Abstract. The field of experimental positronium physics has advanced significantly in the last few decades, with new areas of research driven by the development of techniques for trapping and manipulating positrons using Surko-type buffer gas traps. Large numbers of positrons (typically ≥10 6 ) accumulated in such a device may be ejected all at once, so as to generate an intense pulse. Standard bunching techniques can produce pulses with ns (mm) temporal (spatial) beam profiles. These pulses can be converted into a dilute Ps gas in vacuum with densities on the order of 10 7 cm −3 which can be probed by standard ns pulsed laser systems. This allows for the efficient production of excited Ps states, including long-lived Rydberg states, which in turn facilitates numerous experimental programs, such as precision optical and microwave spectroscopy of Ps, the application of Stark deceleration methods to guide, decelerate and focus Rydberg Ps beams, and studies of the interactions of such beams with other atomic and molecular species. These methods are also applicable to antihydrogen production and spectroscopic studies of energy levels and resonances in positronium ions and molecules. A summary of recent progress in this area will be given, with the objective of providing an overview of the field as it currently exists, and a brief discussion of some future directions.

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Section: Bose-einstein Condensationmentioning

confidence: 99%

Experimental progress in positronium laser physics

2018

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“…(6). However, they only lead to mere shifts in the one-particle dispersions ε e k and ε h k , since spinless electrons and holes as well as a wave-vector independent Coulomb coupling U are considered in model (1).…”

Section: Exciton-polariton Modelmentioning

confidence: 99%

“…Here ω and k denote the energy and momentum transfer. The left panels display the (dominant) coherent contributions (C4), resulting from electron-hole pair annihilation and creation processes inside and in between the fully renormalized quasiparticle bandsẼ mation of an exciton-polariton condensate 6 . If the cavity frequency and the detuning are very large, a coherent signal for the excitonic polarization is obtained for negative ω only.…”

Section: B Spectral Propertiesmentioning

confidence: 99%

Ground-state and spectral signatures of cavity exciton-polariton condensates

2016

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We propose a projector-based renormalization framework to study exciton-polariton Bose-Einstein condensation in a microcavity matter-light system. Treating Coulomb interaction and electronhole/photon coupling effects on an equal footing, we analyze the ground-state properties of the exciton-polariton model according to the detuning and the excitation density. We demonstrate that the condensate by its nature shows a crossover from an excitonic insulator (of Bose-Einstein, respectively, BCS type) to a polariton and finally photonic condensed state as the excitation density increases at large detuning. If the detuning is weak, polariton or photonic phases dominate. While in both cases a notable renormalization of the quasiparticle band structure occurs that strongly affects the coherent part of the excitonic luminescence, the incoherent wave-vector-resolved luminescence spectrum develops a flat bottom only for small detuning.

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“…Since the condensation of hetero pairs is also discussed in, for example, an exciton gas [59][60][61][62][63], an exciton-polariton gas [64][65][66][67], as well as a dense quark matter [68,69], the realization of a superfluid 6 Li-40 K Fermi gas would give great impact on these fields.…”

Section: Introductionmentioning

confidence: 99%

Heteropairing and component-dependent pseudogap phenomena in an ultracold Fermi gas with different species with different masses

Hanai

Ōhashi

2014

Phys. Rev. A

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We investigate the superfluid phase transition and single-particle excitations in the BCS (BareenCooper-Schrieffer)-BEC (Bose-Einstein condensation) crossover regime of an ultracold Fermi gas with mass imbalance. In our recent paper [R. Hanai, et. al., Phys. Rev. A 88, 053621 (2013)we showed that an extended T -matrix approximation (ETMA) can overcome the serious problem known in the ordinary (non-self-consistent) T -matrix approximation that it unphysically gives double-valued superfluid phase transition temperature T c in the presence of mass imbalance. However, at the same time, the ETMA was also found to give the vanishing T c in the weak-coupling and highly mass-imbalanced case. In this paper, we inspect the correctness of this ETMA result, using the self-consistent T -matrix approximation (SCTMA). We show that the vanishing T c is an artifact of the ETMA, coming from an internal inconsistency of this theory. The superfluid phase transition actually always occurs, irrespective of the ratio of mass imbalance. We also apply the SCTMA to the pseudogap problem in a mass-imbalanced Fermi gas. We show that pairing fluctuations induce different pseudogap phenomena between the the light component and heavy component. We also point out that a 6 Li-40 K mixture is a useful system for the realization of a hetero pairing state, as well as for the study of component-dependent pseudogap phenomena.

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Condensation of excitons in Cu₂O at ultracold temperatures: experiment and theory

Cited by 41 publications

References 73 publications

Experimental progress in positronium laser physics

Experimental progress in positronium laser physics

Ground-state and spectral signatures of cavity exciton-polariton condensates

Heteropairing and component-dependent pseudogap phenomena in an ultracold Fermi gas with different species with different masses

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Condensation of excitons in Cu2O at ultracold temperatures: experiment and theory

Cited by 41 publications

References 73 publications

Experimental progress in positronium laser physics

Experimental progress in positronium laser physics

Ground-state and spectral signatures of cavity exciton-polariton condensates

Heteropairing and component-dependent pseudogap phenomena in an ultracold Fermi gas with different species with different masses

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Condensation of excitons in Cu₂O at ultracold temperatures: experiment and theory