Spin excitations in an all-organic double quantum dot molecule

Abstract

We realize a strongly coupled double quantum dot in a single all-organic molecule by introducing a non-conjugated bridge in between two identical conjugated moieties. Spin-1/2 Kondo and Kondo enhanced low-energy excitations for respectively the odd and even electron occupation are observed in off-resonant transport. The ground state in the even occupation can be the singlet or the triplet state varying between samples. This observation suggests that both anti-ferromagnetic and ferromagnetic interactions between spins are of the same order of magnitude.

Environment-assisted quantum transport through single-molecule junctions

“…The bonding and antibonding MOs both lie above the Fermi energy and will henceforth be referred to as the LUMO and LUMO+1 respectively 29 . The choice of the site energies above is not of critical importance, particularly since many currently available experimental techniques allow electrostatic control of the molecular energy levels through a gate electrode 20,[30][31][32] . We begin by considering transport in the absence of any vibrational coupling.…”

“…The two-site character of the molecule can be most easily achieved by breaking the conjugation within the system (introducing regions of low π-electron density). Several structures of this type have recently been investigated in the transport setting [16][17][18][19][20][21] ; the model used here is inspired by the experimental studies of Perrin et al 17,18 . We now proceed to describe the Hamiltonian governing our system (with = 1 and e = 1 throughout).…”

Charge transport through extended molecular wires with strongly correlated electrons

“…In extended molecular systems, more intricate interacting approaches such as the fermionic Hubbard model that account for electron-electron interactions beyond the observation of Coulomb blockade [8][9][10][11][12][13][14][15] are important in describing experimental results. [16][17][18] The Hubbard model is a ubiquitous description of strongly correlated condensed matter systems, including hightemperature superconductors and topological insulators. From a molecular perspective, the fermionic Hubbard model is an extension to the non-interacting Hückel model, which has been used very successfully in combination with Landauer theory to describe off-resonance quantum transport through extended molecules, but fails in the resonant transport regime where electron-electron interactions become dominant.…”

Non-equilibrium thermodynamics in a single-molecule quantum system

“…The Hubbard Hamiltonian, despite its apparent simplicity, can describe a rich variety of correlated-electronic effects from magnetism to superconductivity [38], and has been used effectively to model charge transport through molecular and nanoelectronic systems [39,40]. For a two-site system, that we describe here and was studied in [30] the Hubbard Hamiltonian can be solved exactly.…”