Pushing the limits of the reaction-coordinate mapping

Area of Science:

• Quantum mechanics
• Thermodynamics
• Condensed matter physics

Background:

• Reaction-coordinate mapping simplifies complex quantum systems by augmenting them with a collective environmental coordinate.
• This technique typically relies on weak residual coupling to a simpler reservoir.
• Its applicability in strong-coupling regimes remains largely unexplored.

Purpose of the Study:

• Investigate the validity of reaction-coordinate mapping under strong residual dissipation.
• Analyze its accuracy for heat transport in a quantum system.
• Identify potential limitations and crucial observations for strong-coupling quantum thermodynamics.

Main Methods:

• Developed an exactly solvable model for heat transport in a two-node quantum wire connecting two baths.
• Applied reaction-coordinate mapping with a structured spectral density at the interface.
• Derived a perturbative master equation for the augmented system under strong residual dissipation.

Main Results:

• Accurate prediction of the original problem's stationary state using weak-coupling treatment, even with very strong residual dissipation.
• Sustained agreement throughout the dynamics in the overdamped regime under large residual dissipation.
• Gross overestimation of stationary heat current by the master equation, despite faithful capture of the nonequilibrium steady state.

Conclusions:

• Reaction-coordinate mapping can accurately capture steady states in strong-coupling regimes.
• The method may fail to accurately predict transport properties like heat current.
• Findings are crucial for studying the strong-coupling regime in quantum thermodynamics.