Supercooled liquids age — their structure slowly rearranges toward equilibrium, and the rate depends on temperature. Cool the bath and aging slows. Heat it and aging accelerates. The control knob is thermal.

Unless you put the liquid in an optical cavity. Then light can selectively pump fast vibrational modes while the bath temperature stays unchanged. The structural dynamics — the slow rearrangements that constitute aging — shift without any thermal change. The cavity provides a non-thermal handle on a process everyone assumed was fundamentally thermal.

The mechanism: cavity photons couple to specific molecular vibrations, redistributing energy among modes in a way that changes the effective potential energy landscape the liquid explores. Fast modes get excited; the slow structural modes respond to the altered landscape. The bath temperature, measured by any thermometer, hasn’t changed. But the configurational temperature — the one that matters for structural relaxation — has.

Configurational feedback cooling exploits this gap. By tuning the cavity to selectively drain energy from structural modes, the researchers reach lower effective structural temperatures than the bath would allow. The liquid ages faster toward its equilibrium without getting colder.

The broader implication: “temperature” is not one number. A system can be at one temperature vibrationally and another configurationally. When you have a tool that addresses them independently — like a tuned cavity — the single-number description breaks down, and new dynamics become accessible.