Geometry-induced local thermal current from cold to hot in a classical harmonic system

Area of Science:

• Thermodynamics
• Statistical Mechanics
• Condensed Matter Physics

Background:

• The second law of thermodynamics dictates that overall heat transfer occurs from hotter to colder regions.
• However, local deviations from this macroscopic trend are theoretically possible under specific conditions.
• Understanding these local thermal phenomena is crucial for developing advanced thermal management systems.

Purpose of the Study:

• To investigate the possibility of a local thermal current flowing against the macroscopic temperature gradient.
• To explore the controllability and robustness of such an atypical thermal current.
• To assess the potential applications of this phenomenon in nanoscale systems.

Main Methods:

• Coupling a three-mass harmonic system to two Langevin reservoirs at different temperatures.
• Analyzing the steady-state behavior of thermal currents under varying system parameters.
• Investigating the influence of nonlinear system-substrate coupling on the local thermal current.

Main Results:

• A local thermal current flowing from cold to hot was observed in the steady state, while the overall current remained from hot to cold.
• The direction and magnitude of this local current are tunable via system parameters like mass and coupling strength.
• The atypical thermal current persists even with nonlinear potentials and is robust against system asymmetries.

Conclusions:

• Local thermal currents can flow against the macroscopic temperature gradient, challenging simple interpretations of the second law of thermodynamics.
• The controllability and robustness of this phenomenon suggest potential for novel applications in thermal management and information storage.
• This study opens avenues for designing nanoscale devices with tailored thermal transport properties.