Quantum descriptions of many complex systems are formulated most naturally in bases of states that are not mutually orthogonal. We introduce a general and powerful yet simple approach that facilitates solving such models exactly by embedding the nonorthogonal states into a new Hilbert space in which they are by definition mutually orthogonal. This novel approach is applied to electronic transport in molecular quantum wires and is used to predict conductance antiresonances of a new type that arise solely out of the nonorthogonality of the local orbitals on different sites of the wire.

• Received 27 July 1998

DOI:https://doi.org/10.1103/PhysRevLett.81.5205