Quantum Noise of Current in a 1,4-Benzenedithiol Single-Molecule Junction: First-Principle Calculations

Shot noise refers to the autocorrelation of current related to the quantum statistics of discrete electrons. The
study of shot noise can provide a deep understanding of the quantum fluctuation of current, owing to the interference between
incident and reflected electrons. Electrons experience scattering when in the mesoscopic quantum point contact with materials
of intermediate lengths. Thus, electron transport is typically incoherent and quantum channels are reformed in leads through
adiabatic constriction. The starting point of the shot noise theory is based on a field operator constructed from incoherent wave
functions in leads. However, electron transport is coherent in single-molecule junctions with length scales smaller than the
dephasing length. In investigations regarding shot noise in systems with coherent electron transport, using a field operator
constructed from coherent wave functions is natural. In this study, we investigated shot noise in a 1,4-benzenedithiol singlemolecule junction on the basis of coherent wave functions obtained self-consistently from first-principles approaches. The
theoretical value of shot noise in our calculations is S ≈ 4.03 × 10−26 A2
/Hz at VBias = 0.01 V. This value is in good agreement
with that obtained from a recent experimental measurement (S ≈ 4.37 × 10−26 A2
/Hz).