Our aims are to:
- explore the limits of transistor operation near atomic scale limits
- develop the appropriate theoretical framework to describe the quantum properties of charge transport at the molecular scale,
- predict unimolecular electrical signals via accurate simulations,
- identify tuneable effects with the additional characterisation of the electronic structure of different types of molecules from first-principles.
Correlated electron transport for molecular electronics
By reformulating the transport problem using boundary conditions suitable for correlated many-electron systems, we have approached electron transport across molecules from a new standpoint. Application of our correlated formalism to benzene-dithiol gives current-voltage characteristics close to experimental observations. The method can solve the open system quantum many-body problem accurately, treats spin exactly and is valid beyond the linear response regime. We work directly with many-body wavefunctions and the exact molecular electronic Hamiltonian using the configuration interaction (CI) formalism which can give accurate solutions with an equal treatment of ground and excited electronic states. Click here for the calculated current-voltage relationship
Many-body picture of tunnelling and independent particle models
Tunnelling currents across thin insulators are commonly described as electrons moving in the forbidden energy domain of an effective potential. Electron tunnelling is examined from a different perspective by explicit treatment of electron-electron interactions on a many-body footing allowing for the validity of independent particle models to be determined, and for correlation contributions to the current to be quantified. Our results agree well with measurements across alkane oligomers and clarify the role of electron correlation in non-resonant tunnelling. Maximizing the overlap with the current-carrying state rather than minimizing the energy as in the Hartree-Fock theory is most suitable for single-particle approximations in a system with open boundary conditions.
Tunnel resistance-increase exponential law