Single-electron transistors in electromagnetic environments

TL;DR

This paper investigates how electromagnetic environments, manipulated via SQUID arrays, affect the behavior of single-electron transistors, revealing tunable Coulomb blockade effects and charge modulation in different states.

Contribution

It demonstrates the impact of high-impedance environments on SETs and introduces a method to control Coulomb blockade and charge periodicity using SQUID arrays.

Findings

Effective charging energy increases in high-impedance environments.

Sharp Coulomb blockade observed when SQUID array impedance exceeds R_K.

Transition from e to 2e periodicity in charge modulation.

Abstract

The current-voltage (I-V) characteristics of single-electron transistors (SETs) have been measured in various electromagnetic environments. Some SETs were biased with one-dimensional arrays of dc superconducting quantum interference devices (SQUIDs). The purpose was to provide the SETs with a magnetic-field-tunable environment in the superconducting state, and a high-impedance environment in the normal state. The comparison of SETs with SQUID arrays and those without arrays in the normal state confirmed that the effective charging energy of SETs in the normal state becomes larger in the high-impedance environment, as expected theoretically. In SETs with SQUID arrays in the superconducting state, as the zero-bias resistance of the SQUID arrays was increased to be much larger than the quantum resistance R_K = h/e^2 = 26 kohm, a sharp Coulomb blockade was induced, and the current modulation by the gate-induced charge was changed from e periodic to 2e periodic at a bias point 0<|V|<2D_0/e, where D_0 is the superconducting energy gap. The author discusses the Coulomb blockade and its dependence on the gate-induced charge in terms of the single Josephson junction with gate-tunable junction capacitance.