Spatial coherence in an exciton-polariton condensate developed in two stages, the study reports. It first showed growth, partial collapse and revival, then entered a quasi-steady regime with maximal coherence extending across the condensate.
The work examined how a driven-dissipative condensate forms over time after a quench, or sudden disturbance, using time-resolved experiments and numerical modeling. Here, spatial coherence refers to how closely light emitted from different parts of the condensate remains related.
Two ways to make the disturbance
Researchers created the quench in two configurations. RPL used pulsed off-resonant ring excitation. GCW used a Gaussian condensate under continuous pumping that was briefly disrupted by a pulse and then re-formed under continuous-wave excitation.
Time-resolved photoluminescence measurements used a streak camera and spectrometer to capture the condensate's distribution and energy. A Michelson interferometer measured its first-order spatial correlation, g(1), the quantity used to track coherence. The numerical analysis used coupled polariton mean-field and excitonic-reservoir equations, the truncated-Wigner approximation and one spatial dimension for both configurations.
The experimental systems were high-quality planar microcavities with embedded GaAs quantum wells that host excitons.
The early pattern varied across the tests
Both configurations showed the same broad sequence: transient coherence oscillations came first, followed by quasi-steady coherence. The two experiments were performed by independent research groups at different locations.
In RPL, the transient oscillatory regime was absent at pump power below four times the threshold, appeared above four times threshold, and occurred earlier with multiple rise-and-decay periods above ten times threshold. The transition from the transient regime to the quasi-steady regime changed little across that pump-power sweep.
In GCW, stronger breaking-pulse settings were associated with the emergence of transient g(1) oscillations and with more pronounced oscillations. The initial depletion of the condensate changed little once the breaking threshold was exceeded.
The study also compared the excitonic fraction, the proportion of exciton character in the polariton state. At 0.38, the lowest tested fraction, a single coherence oscillation was recorded; at higher tested fractions, the recorded pattern contained twice as many oscillations and was more sharply defined.
A coherent state larger than the condensate
By the later quasi-steady stage, coherence was maximal across the condensate. At 504 picoseconds, fitting the spatial-correlation profile gave a coherence length of 921 micrometres, more than 20 times the condensate's diameter. The fitted range was therefore much larger than the condensate itself.
The 921-micrometre result is a fitted point estimate. The report gives no fit interval or formal uncertainty estimate alongside it.
A possible explanation, with a clear limit
High-pump simulations showed g(1) oscillations and oscillations in the population of the lowest energy mode in phase with changing ratios of populations across the modes. The authors interpreted this co-occurrence as redistribution among polariton modes after the quench. The timing is an association between signals, not randomized causal identification, and it does not establish redistribution as the only possible mechanism.
A supplemental sloshing-condensate test also produced g(1) oscillations, but it did not reproduce the structured combination of the transient and quasi-steady regimes. Visibility was generally lower, and the oscillations continued until the condensate fully decayed.
The test addressed the sloshing scenario examined in the study; it was not a test of every possible explanation for the oscillations.
What the evidence covers
The direct experimental evidence is limited to non-equilibrium exciton-polariton condensates in the studied GaAs microcavities and the two quench configurations. The numerical model was one-dimensional, and whether the same two-stage pathway occurs in other driven bosonic systems remains untested.
The parameter comparisons and the coherence-length fit were reported without formal uncertainty estimates, confidence intervals, p-values or statistical hypothesis tests.
This is arXiv version 1, dated 26 August 2026.
Paper data and sources
Original title: Dynamical development of long-range spatial coherence in non-equilibrium bosonic condensation
Authors: Bianca Rae Fabricante, Dąbrówka Biegańska, Paolo Comaron et al.
Journal/Repository: arXiv
Status: Preprint, not yet peer-reviewed
First online: 2026-08-26
DOI: Not available
Original paper · Full text