# Chiral Prethermalization in Split Condensates
⏎
**Anchor paper:** K. Agarwal, E.G. Dalla Torre, B. Rauer, T. Langen, J. Schmiedmayer, E. Demler, "Chiral prethermalization in supersonically split condensates," *Phys. Rev. Lett.* 113, 190401 (2014). [arXiv:1402.6716]
⏎
## Background
In 1D quasicondensates, splitting a condensate into two coherently coupled halves and letting them dephase produces a well-studied "prethermal" state, with phase correlations settling into an effective-temperature description (confirmed in Schmiedmayer-group atom-chip experiments). This picture assumed a gentle split, creating left- and right-moving phonon-like excitations symmetrically, equilibrating to one common effective temperature. Open question: what happens when the splitting perturbation itself moves *supersonically* — faster than the speed of sound — as in realistic finite-time chip-based splitting, potentially outrunning and asymmetrically imprinting the two counter-propagating phonon branches?
⏎
## New results
A supersonic "unzipping" of a 1D condensate produces a qualitatively new, *chiral* prethermal state: right- and left-moving Bogoliubov excitations acquire different, Doppler-shifted effective temperatures rather than relaxing to one shared value, following a Lorentz-boost-like relation set by the splitting and release velocities. This chirality is readable via fringe contrast at a supersonically-moving release point, and an accelerating release point was predicted to reveal a spacelike analog of the Unruh effect. The authors draw a direct analogy to the CMB dipole anisotropy, where relative motion through an isotropic thermal bath produces an apparent directional temperature difference via Doppler shifting — framing chiral prethermalization as a table-top realization of that same relativistic-kinematic effect.
⏎
![Supersonic condensate-splitting protocol schematic](https://arxiv.org/html/1402.6716v1/protocol3.png)
*Schematic of the protocol: a 1D condensate is coherently split at supersonic velocity v_s, evolves freely, then is released at supersonic velocity v_r, with resulting fringe contrast revealing the chiral, Doppler-shifted prethermal temperatures.*
⏎
## Related work in this direction
- K. Agarwal, E.G. Dalla Torre, J. Schmiedmayer, E. Demler, "Quantum heat waves in a one-dimensional condensate," PRB 95, 195157 (2017) — extends this framework by studying how the asymmetric phonon populations manifest as propagating heat-wave signatures and thermal transport.
⏎
⏎
# Parents
⏎
* Engineered Spacetime Quenches for Critical-State Preparation⏎