Sensitivity of a DC SQUID with a non-sinusoidal current-phase relation in its junctions

Prance, Jonathan and Thompson, Michael (2023) Sensitivity of a DC SQUID with a non-sinusoidal current-phase relation in its junctions. Applied Physics Letters, 122 (22). ISSN 0003-6951

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Abstract

In ballistic superconductor–normal metal–superconductor Josephson junctions, such as those made from graphene or high mobility semiconductors, the current-phase relation may not have the common, sinusoidal form but can be skewed to have a peak supercurrent at a phase difference greater than π/2⁠. Here, we use a numerical simulation that includes thermal noise to investigate the sensitivity of a DC superconducting quantum interference device (SQUID) with such junctions. The simulation uses a resistively and capacitively shunted junction model where the current-phase relation of each junction can be defined as an arbitrary function. The modulation, transfer function, noise, and sensitivity of a SQUID are calculated for different types of current-phase relation. For the examples considered here, we find that the flux sensitivity of the SQUID is always degraded by forward skewing of the current-phase relation, even in cases where the transfer function of the SQUID has been improved.