Green's function methods for single molecule junctions

Area of Science:

• Quantum Mechanics
• Condensed Matter Physics
• Molecular Electronics

Background:

• Experimental advances in molecular electronics have spurred theoretical interest.
• Understanding open quantum systems out of equilibrium is crucial.
• Green's function methods are powerful tools for theoretical analysis.

Purpose of the Study:

• To provide a pedagogical review of theoretical Green's function methods.
• To focus on applications to single molecule junctions.
• To discuss various theoretical approaches for analyzing these systems.

Main Methods:

• Review of standard nonequilibrium Green's function (NEGF) method.
• Discussion of many-body flavors like pseudoparticle and Hubbard NEGF.
• Introduction to the superperturbation dual fermion approach for intermediate regimes.
• Overview of numerically exact methods based on Green's functions.

Main Results:

• Identified two characteristic energy scales: many-body interactions and molecule-contact coupling.
• Demonstrated the utility of NEGF for weak interactions and coupling.
• Showcased the superperturbation dual fermion approach for comparable energy scales.
• Highlighted recent developments in numerically exact Green's function methods.

Conclusions:

• Green's function methods offer versatile approaches for studying open quantum systems.
• Specific methods are well-suited for different regimes of interaction and coupling.
• Advanced numerical techniques are extending the applicability of Green's functions to complex systems.