Dynamical symmetries and quantum transport through nanostructures

Abstract

We discuss the manifestation of dynamical symmetries in quantum transport through nanostructures. The dynamical symmetry SO(4) manifested in the singlet-triplet excitations is shown to be responsible for several exotic effects in nano-devices: non-equilibrium Kondo effect in T-shape Double Quantum Dots, phonon-induced Kondo effect in transition-metal-organic complexes, Kondo shuttling in Nano-Electromechanical Single Electron Transistor. We consider the interplay between charge U (1) and spin SU (2) fluctuations in the vicinity of Stoner instability point and a non-monotonic behavior of a Tunneling Density of States in metallic quantum dots. The experiments showing important role of dynamical symmetries in nanostructures are briefly reviewed.

Electronic and magnetic properties of molecule-metal interfaces: Transition-metal phthalocyanines adsorbed on Ag(100)

“…74,75 In Kondo systems, the coherent coupling of the Kondo state with such excitations leads to additional peaks at the energies of the inelastic conductance steps. 76 Unlike quantum dots, where the reduced orbital level-spacing favors the coupling of Kondo and electronic excitations, 77 the origin of such side peaks in small aromatic molecules is restrained to vibrational 41,78-80 (K v ) or magnetic 39,73,[81][82][83] (K ts ) excitations. In the present case, by comparing the energy of the K v peaks with that of the Raman vibrational modes of gas-phase CuPc, 84 we find that the inelastic features found at the position of the Ni and Cu ions [Fig.…”

Spin coupling and relaxation inside molecule–metal contacts

“…The fingerprints of this interaction are the two side peaks observed at E Kts = ± 21 meV ( ± 1 meV) in the dI/dV spectrum of CuPc, which are absent in NiPc (Figs 1b and 2a). In Kondo systems, such side peaks are assigned to cotunnelling events that involve coherent Kondo spin-flips and inelastic excitations 31 . Unlike quantum dots, where the reduced orbital level-spacing may favour the coupling of Kondo and electronic excitations 32,33 , the origin of such side peaks in small aromatic molecules is restrained to vibrational 5,27,29 or magnetic [34][35][36] excitations, as schematized in Figure 4a.…”