Steady-state non-equilibrium numerical renormalization group approach applied to molecular electronics
Final Report Abstract
(i) We investigated the phase space of a strongly correlated two-orbital model to address the emerging and screening of magnetic moments in the vicinity of Carbon vacancies in graphene close to the charge neutrality point. The local curvature of the graphene sheet strongly influence the local dynamics: Depending on the coupling strength, we identified three classes of spectral response and linked them to the different regimes found in the scanning tunneling spectra. Two papers with an international collaboration of theorists from Taiwan and experimentalists at Rutgers, NJ, USA, were published: one paper in Nature Communications and one paper in Physical Review B, highlighted by the Physical Review B (PRB) as Editors’ suggestion. (ii) Using Hershfield’s description of the non-equilibrium steady state density operator, we investigated the robustness of quantum transport in helical edge states of topological insulator. We have proven that the backscattering current vanishes in an U (1) gauge symmetric problem. This symmetry can be broken by an local anisotropic magnetic interaction while time-reversal symmetry remains preserved. Using perturbative RG arguments as well as a full non-equilibrium scattering states numerical renormalization group (NRG) calculation we showed that the U (1) symmetry is asymptotically restored by the Kondo effect. One paper was published in PRB on this subject. (iii) We developed a novel many-body approach to inelastic tunneling spectroscopy. This theory was applied to the quantum-transport through the organic NTCDA molecules on a clear Ag(111) surface. Two different types of stable locations of the organic molecule on a Ag surface were experimentally found and characterised by density functional theory (DFT). Our theory is able to predict the correct Kondo temperature using the DFT results as input. We also provided a deeper understanding of the inelastic features in the differential conductance. One paper was published on this sub-project, highlighted by the Physical Review B as Editors’ suggestion. (iv) The PhD student funded by the project implemented a novel steady-state non-equilibrium numerical renormalization group approach and investigated its properties. For a non-interacting problem, the pseudo-equilibrium approach reproduces the established I-V curve obtained via Keldysh formalism for the full continuum problem. He also found Coulomb blockade physics for an interacting nano-junction at intermediate temperature and in the vicinity of the local moment fixed point. However, his approach was not able to access the universal transport regime where the I-V curve become independent on the interaction strength.
Publications
- Inducing Kondo screening of vacancy magnetic moments in graphene with gating and local curvature. Nature Comm. 9, 2349 (2018)
Jinhai Mao, Yuhang Jiang, Po-Wei Lo, Daniel May, Guohong Li, Guang-Yu Guo, Frithjof Anders, Takashi Taniguchi, Kenji Watanabe, Eva Y. Andrei
(See online at https://doi.org/10.1038/s41467-018-04812-6) - Modeling of gate controlled Kondo effect at carbon point-defects in graphene. Phys. Rev. B 97, 155419 (2018)
Daniel May, Po-Wei Lo, Kira Deltenre, Anika Henke, Jinhai Mao, Yuhang Jiang, Guohong Li, Eva Y. Andrei, Guang-Yu Guo, and Frithjof B. Anders
(See online at https://doi.org/10.1103/PhysRevB.97.155419) - Analytical and numerical study of the out-of-equilibrium current through a helical edge coupled to a magnetic impurity, Phys. Rev. B 101, 165112 (2020)
Yuval Vinkler-Aviv, Daniel May, and Frithjof B. Anders
(See online at https://doi.org/10.1103/PhysRevB.101.165112) - Inelastic electron tunneling spectroscopy for probing strongly correlated many-body systems by scanning tunneling microscopy, Phys. Rev. B 101, 125405 (2020)
Fabian Eickhoff, Elena Kolodzeiski, Taner Esat, Norman Fournier, Christian Wagner, Thorsten Deilmann, Ruslan Temirov, Michael Rohlfing, F. Stefan Tautz, and Frithjof B. Anders
(See online at https://doi.org/10.1103/PhysRevB.101.125405)
