Experimental Evidence for Coulomb Charging Effects in the Submicron Bi-2212 Stacks

TL;DR

This study demonstrates Coulomb charging effects in submicron Bi-2212 stacks, revealing Coulomb blockade phenomena that alter their electrical characteristics compared to larger junctions.

Contribution

The paper introduces a fabrication method for submicron Bi-2212 stacks and provides experimental evidence of Coulomb blockade effects in these nanoscale junctions.

Findings

Suppressed critical current density in submicron stacks

Elimination of hysteresis and multibranched IV features

Reproducible periodic current peaks consistent with Coulomb charging energy

Abstract

We developed the focused ion beam (FIB) and ion milling techniques for a fabrication of the Bi_2Sr_2CaCu_2O_{8+\delta} (Bi-2212) stacked junctions with in-plane size L_{ab} from several microns down to the submicron scale without degradation of T_c. We found that behaviour of submicron junctions (L_{ab} < 1 {\mu}m) is quite different from the bigger ones. The critical current density is considerably suppressed, the hysteresis and multibranched structure of the IV characteristics are eliminated, the periodic structure of current peaks reproducibly appears on the IV curves at low temperatures. A period of the structure, {\Delta}V, is consistent with the Coulomb charging energy of a single pair, {\Delta}V = e/C with C the effective capacitance of the stack. We consider this behaviour to originate from the Coulomb blockade of the intrinsic Josephson tunneling in submicron Bi-2212 stacks.