Bloch diode

TL;DR

This paper predicts a dual to the Josephson diode effect, called the Bloch diode effect, in a gate-tunable Cooper pair transistor with asymmetrical Bloch band dispersion, enabled by a resistive environment.

Contribution

It introduces the concept of the Bloch diode effect as a dual to the Josephson diode effect, based on asymmetries in Bloch band dispersion in superconducting circuits.

Findings

Predicts the Bloch diode effect in a Cooper pair transistor.

Shows the effect arises from asymmetry in Bloch band dispersion.

Suggests implementation using conventional superconducting circuits.

Abstract

In a SQUID tuned away from half-integer flux (in units of the superconducting flux quantum), the concurrence of multiple Josephson harmonics and an asymmetry between the junctions leads to the Josephson diode effect -- a nonreciprocal current-voltage characteristic manifested as an asymmetry of critical currents at opposite polarities. We predict a dual version of this effect in a gate-tunable Cooper pair transistor placed in series with a highly resistive environment. When tuned away from half-integer gate charge (in units of the Cooper pair charge) it shows an asymmetry of critical voltages at opposite polarities -- a dual diode effect we refer to as the Bloch diode effect. It arises from an asymmetry in the dispersion of the transistor's Bloch bands. A highly resistive environment can be realized with a Josephson junction array, suggesting that such a diode could be implemented using conventional superconducting quantum circuits.