Effects of electron-phonon coupling in the Kondo regime of a two-orbital molecule

Abstract

We study the interplay between strong electron-electron and electron-phonon interactions within a two-orbital molecule coupled to metallic leads, taking into account Holstein-like coupling of a local phonon mode to the molecular charge as well as phonon-mediated interorbital tunneling. By combining canonical transformations with numerical renormalization-group calculations to address the interactions nonperturbatively and on equal footing, we obtain a comprehensive description of the system's many-body physics in the anti-adiabatic regime where the phonons adjust rapidly to changes in the orbital occupancies, and are thereby able to strongly affect the Kondo physics. The electron-phonon interactions strongly modify the bare orbital energies and the Coulomb repulsion between electrons in the molecule, and tend to inhibit tunneling of electrons between the molecule and the leads. The consequences of these effects are considerably more pronounced when both molecular orbitals lie near the Fermi energy of the leads than when only one orbital is active. In situations where a local moment forms on the molecule, there is a crossover with increasing electron-phonon coupling from a regime of collective Kondo screening of the moment to a limit of local phonon quenching. At low temperatures, this crossover is associated with a rapid increase in the electronic occupancy of the molecule as well as a marked drop in the linear electrical conductance through the single-molecule junction.

17 pages, 13 figures

References in corpus (17)

• The numerical renormalization group method for quantum impurity systems
• Molecular Transport Junctions: Vibrational Effects
• Inelastic electron tunneling via molecular vibrations in single-molecule transistors
• Quantum phase transition in a single-molecule quantum dot
• Tuning the Kondo effect with a mechanically controllable break junction
• Resonant Electron Transport in Single-Molecule Junctions: Vibrational Excitation, Rectification, Negative Differential Resistance and Local Cooling
• Many Body Effects on the Transport Properties of Single-Molecule Devices
• Vibrational Sidebands and Kondo-effect in Molecular Transistors
• Evolution of SU(4) Transport Regimes in Carbon Nanotube Quantum Dots
• Quantum transport through a deformable molecular transistor
• Correlated electron physics in multilevel quantum dots: phase transitions, transport, and experiment
• Electronic Transport through Magnetic Molecules with Soft Vibrating Modes
• Phonon-assisted tunneling and two-channel Kondo physics in molecular junctions
• Kondo effect and channel mixing in oscillating molecules
• Conductance of a molecule with a center of mass motion
• Slave boson theory for transport through magnetic molecules with vibronic states
• Phonon-assisted tunneling regimes in diatomic molecules