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Abnormal heating in a colloidal system

Importance

A cold system normally takes longer to warm up than a cold system. However, recent theoretical studies suggest that the reverse is sometimes possible. Here, using a colloidal particle in a heat bath, we present experimental evidence for this inverse Mpemba effect. By carefully choosing the energy landscape, we can cause the cold system to heat up exponentially faster than the rate at which cold systems heat up. While similar behavior has been observed in systems that are cooling – the Mpemba effect – we find that entropic effects generally make anomalous heating harder to observe than anomalous cooling.

Summary

We report anomalous heating in a colloidal system, an experimental observation of the inverse Mpemba effect, where for two initial temperatures below the temperature of the thermal bath, the colder of the two systems heats up faster when coupled to the same bath. thermal. For an overdamped Brownian colloidal particle moving in an inclined double-well potential, we find a non-monotonic dependence of the heating times on the initial temperature of the system. Entropic effects make the inverse Mpemba effect generically weaker – harder to observe – than the usual Mpemba effect (abnormal cooling). We also observe a strong version of anomalous heating, where a cold system heats up exponentially faster than systems prepared under slightly different conditions.