Thermodynamic free-energy spectrum theory for open quantum systems

Area of Science:

• Quantum thermodynamics
• Condensed matter physics
• Statistical mechanics

Background:

• Open quantum systems describe interactions between a quantum system and its environment.
• Understanding the thermodynamics of such systems is crucial for quantum technologies.
• Quantum impurity systems, like quantum dots, are fundamental models in condensed matter.

Purpose of the Study:

• Develop a free-energy spectrum theory for open quantum impurity systems (fermionic, bosonic, or combined).
• Identify and analyze thermodynamic free-energy spectral functions.
• Relate these functions to experimentally measurable local impurity properties.

Main Methods:

• Formulation of the free-energy spectrum theory.
• Identification of two types of thermodynamic free-energy spectral functions.
• Consideration of the thermodynamic limit and Gaussian-Wick description for hybrid environments.
• Analysis of bare-bath coupling spectral densities.
• Illustration using simplest noninteracting systems (bosonic vs. fermionic).

Main Results:

• The theory provides a framework for thermodynamics of diverse open quantum impurity systems.
• Two distinct thermodynamic free-energy spectral functions are identified.
• A connection is established between thermodynamic spectral functions and local impurity properties.
• The study highlights significant differences between bosonic and fermionic system characteristics.

Conclusions:

• The developed free-energy spectrum theory offers a robust tool for studying open quantum impurity systems.
• The findings facilitate the interpretation of experimental measurements, particularly for quantum dots.
• The theory's applicability extends to various quantum systems, including those with hybrid environments.