Electron Transfer Methods in Open Systems.

Area of Science:

• Quantum mechanics
• Condensed matter physics
• Materials science

Background:

• Electron transfer methods are widely used for quantum transport due to their simplicity.
• Existing models often rely on simplified Golden Rule expressions, necessitating more advanced approaches.
• Previous kinetic schemes for quantum transport have limitations beyond second-order Lindblad/Redfield considerations.

Purpose of the Study:

• To analyze the construction of rates in open quantum systems using a novel diagrammatic technique.
• To demonstrate how established rate expressions emerge as specific cases within a more general framework.
• To highlight the advantages of the Hubbard Green's function approach for developing generalized rate expressions.

Main Methods:

• Utilizing the recently introduced nonequilibrium Hubbard Green's function diagrammatic technique.
• Analyzing zero- and second-order Green's function diagrammatic series with bare diagrams.
• Applying standard diagram dressing to incorporate additional baths and degrees of freedom.

Main Results:

• Demonstrated that second- and fourth-order rate considerations are particular cases of zero- and second-order Green's function series.
• Identified limitations of previous rate formulations.
• Showcased the Hubbard Green's function approach as advantageous for constructing quantum transport rates.

Conclusions:

• The Hubbard Green's function method provides a robust framework for deriving generalized rate expressions in open quantum systems.
• Standard diagram dressing naturally accounts for additional baths and degrees of freedom.
• This approach offers a more comprehensive understanding of quantum transport rates beyond traditional methods.