# High-temperature nonequilibrium Bose condensation induced by a hot needle

## TL;DR

This paper theoretically demonstrates that a one-dimensional Bose gas driven far from equilibrium by a hot localized bath can exhibit high-temperature Bose condensation, including into excited states, due to suppression of long-wavelength excitations.

## Contribution

It introduces a novel nonequilibrium setup with a hot needle that induces high-temperature Bose condensation and explores the conditions favoring ground or excited state condensation.

## Key findings

- Bose condensation occurs at temperatures much higher than equilibrium.
- Condensation can shift from ground to excited states with increasing needle temperature.
- Suppression of long-wavelength excitations explains the high-temperature condensation.

## Abstract

We investigate theoretically a one-dimensional ideal Bose gas that is driven into a steady state far from equilibrium via the coupling to two heat baths: a global bath of temperature $T$ and a "hot needle", a bath of temperature $T_h\gg T$ with localized coupling to the system. Remarkably, this system features a crossover to finite-size Bose condensation at temperatures $T$ that are orders of magnitude larger than the equilibrium condensation temperature. This counterintuitive effect is explained by a suppression of long-wavelength excitations resulting from the competition between both baths. Moreover, for sufficiently large needle temperatures ground-state condensation is superseded by condensation into an excited state, which is favored by its weaker coupling to the hot needle. Our results suggest a general strategy for the preparation of quantum degenerate nonequilibrium steady states with unconventional properties and at large temperatures.