Nanothermodynamics: There's plenty of room on the inside

TL;DR

Nanothermodynamics offers a new framework for understanding complex behaviors in small systems, explaining phenomena like critical scaling, noise, and entropy paradoxes through models with orthogonal dynamics and finite-size effects.

Contribution

This review introduces the concept of nanothermodynamics as a unifying approach to explain diverse phenomena in small systems, including entropy, noise, and phase transitions, with novel solutions to classical paradoxes.

Findings

Explains non-classical critical scaling near ferromagnetic transitions.

Describes crossover from white to 1/f noise in materials.

Provides solutions to Gibbs' paradox and Loschmidt's paradox.

Abstract

Nanothermodynamics provides the theoretical foundation for understanding stable distributions of statistically independent subsystems inside larger systems. In this review it is emphasized that adapting ideas from nanothermodynamics to simplistic models improves agreement with the measured properties of many materials. Examples include non-classical critical scaling near ferromagnetic transitions, thermal and dynamic behavior near liquid-glass transitions, and the 1/f-like noise in metal films and qubits. A key feature in several models is to allow separate time steps for distinct conservation laws: one type of step conserves energy and the other conserves momentum (e.g. dipole alignment). This "orthogonal dynamics" explains how the relaxation of a single parameter can exhibit multiple responses such as primary, secondary, and microscopic peaks in the dielectric loss of supercooled liquids, and the crossover in thermal fluctuations from Johnson-Nyquist (white) noise at high frequencies to 1/f-like noise at low frequencies. Nanothermodynamics also provides new insight into three basic questions. First, it gives a novel solution to Gibbs' paradox for the entropy of the semi-classical ideal gas. Second, it yields the stable equilibrium of Ising's original model for finite-sized chains of interacting binary degrees of freedom ("spins"). Third, it confronts Loschmidt's paradox for the arrow of time, showing that an intrinsically irreversible step is required for maximum entropy and the second law of thermodynamics, not only in the thermodynamic limit but also in systems as small as N=2 particles