Origin of apparent low-temperature saturation

Determine whether the apparent low-temperature saturation of resistivity or superfluid stiffness in the InAs/Al Josephson junction arrays results from inadequate electron thermalization and an effective electron temperature higher than the measured sample-stage temperature.

Background

The measurements report finite low-temperature resistance in the anomalous-metal regime and saturation of the measured superfluid stiffness at low temperature. The experiment does not directly measure the electron temperature of the arrays.

The authors perform several heating and wiring-control tests and conclude that their observations strongly suggest a relation to spatial inhomogeneity rather than nonequilibrium effects. Nevertheless, they cannot exclude insufficient thermalization, which could produce an apparent saturation independent of the intrinsic low-temperature physics.

References

We do not have a direct measurement of the electron temperature of our devices, so we cannot definitively rule out the possibility that despite the filtering and thermalization strategies described above, the effective electron temperature is higher than the measured sample stage temperature. Such a failure to thermalize the array below a certain temperature could result in an apparent low temperature saturation of the resistivity and/or superfluid stiffness.

— Imaging how fluctuations destroy superconductivity in two dimensions  (2609.28837 - Horn et al., 23 Sep 2026) in Supplementary Text, subsection “Sample thermalization”