Heat exchanges in a quenched ferromagnet

TL;DR

This paper analytically investigates the distribution of heat exchanged in a quenched ferromagnet, revealing a threshold phenomenon and mode-specific temperature behaviors linked to off-equilibrium dynamics.

Contribution

It provides an exact analytical calculation of the heat distribution in a large-N ferromagnet after a quench, highlighting a singular threshold and mode-dependent temperature effects.

Findings

Existence of a singular heat exchange threshold Qc < 0.

Macroscopic heat release by the zero Fourier mode.

Distinct internal temperatures for different Fourier modes.

Abstract

The off-equilibrium probability distribution of the heat exchanged by a ferromagnet in a time interval after a quench below the critical point is calculated analytically in the large-N limit. The distribution is characterized by a singular threshold Qc < 0, below which a macroscopic fraction of heat is released by the k = 0 Fourier component of the order parameter. The mathematical structure producing this phenomenon is the same responsible of the order parameter condensation in the equilibrium low temperature phase. The heat exchanged by the individual Fourier modes follows a non trivial pattern, with the unstable modes at small wave vectors warming up the modes around a characteristic finite wave vector kM. Two internal temperatures, associated to the k = 0 and k = kM modes, rule the heat currents through a fluctuation relation similar to the one for stationary systems in contact with two thermal reservoirs.