Coulomb blockade related to mutual Coulomb interaction in an external environment in an array of single tunnel junctions connected to Ni nanowires

Abstract

The Coulomb blockade ~CB!, which depends on the mutual Coulomb interaction ~MCI! in external electromagnetic environments ~EME’s!, is reported in an array system of single tunnel junctions connected directly to disordered Ni nanowires ~i.e., an array of a disordered Ni nanowire/Al2O3 /Al system located in parallel!, fabricated using a nanoporous Al film template. The observed zero-bias conductance (G0) anomaly and its linear G0 versus temperature relation qualitatively agree with the CB observations of Zeller and Giaever and of Cleland, Schmidt, and Clarke. The CB is also quantitatively confirmed from the extended Zeller-Giaever model in a tunnel-junction array. In the high-voltage region, only one-dimensional ~1D! MCI following the Altshuler-Aronov formula in a disordered Ni wire dominates the conductance mechanism with the absence of the CB. In contrast, in the lower-voltage region, the CB mentioned above emerges at temperatures below a phase-transition temperature (Tc), accompanied by the 1D MCI in the Ni wire. The MCI plays the key roles of high-impedance EME and transmission line following the phase correlation theory of the CB. It is found that the CB is very sensitive to the diffusion coefficient ~D! of the MCI, resulting in the linear Tc-vs-D 1/2 relation. For this relation, we propose as one possible model, that the charging energy of the CB competes with the energy quantum of fluctuation of the Nyquist phase breaking caused by multiple Coulomb scattering in the Ni nanowire. This linear Tc-vs-D 1/2 relation is reconfirmed by the Ni-wire diameter dependence of Tc . The magnetic field dependence of the G0-versus-temperature relation obviously supports the actual presence of Tc with different conductance mechanisms for the temperatures above and below Tc .