Measurement of energy gaps in superconductors by means of quantum interference devices

TL;DR

This paper experimentally investigates how temperature affects discrete current changes in highly inductive niobium superconductors with point contacts, measuring voltage pulses that relate to the superconductor's energy gap and quantum interference effects.

Contribution

It introduces a method to measure energy gaps in superconductors using quantum interference devices based on voltage pulse characteristics.

Findings

Voltage pulse magnitude approximates the energy gap 2D/e.

Pulse duration (~10-6 s) matches the minimal change time (~10-12 s).

Results support models of quantum interference in doubly-connected superconductors.

Abstract

The effect of temperature on the form of discrete changes in the current in highly inductive (~10-6 H) doubly-connected superconductors with niobium-niobium clamped point contacts is determined experimentally. The magnitude and duration of the voltage pulse on a doubly-connected superconductor is measured at the time of the discrete change in its current state. The pulse magnitude is close to the energy gap 2D/e of the superconductor and its duration (~10-6 s) corresponds to the minimum possible time (~10-12 s) for a change in the state of the contact when the depairing current through it is reached. The measurement data are discussed in terms of models of the quantum interference of currents in a doubly-connected superconductor with clamped point contacts in the form of a quantum interferometer.