Modeling Iridium-Based Trilayer and Bilayer Transition-Edge Sensors

We report a model that can be used to calculate superconducting transition temperature of a transition-edge sensor (TES), which is either a normal metal–superconductor–normal metal trilayer or a normal metal–superconductor bilayer. The model allows the
$T_{C}$
estimation of a trilayer when the normal metals at the bottom and at the top are different. Furthermore, the model includes the spin flip time of the normal metals. We use the
$T_{C}$
calculations from this model for selected Ir-based trilayers and bilayers to help understand potential designs of low
$T_{C}$
TESs. A Au/Ir/Au trilayer can have a low
$T_{C}$
because the superconducting order parameter is reduced with normal metals at both sides. On the other hand, an Ir/Pt bilayer can have a low
$T_{C}$
because the much larger electron density of states of Pt reduces the superconducting order parameter more effectively. Moreover, the spin flip scattering of paramagnetic Pt also contributes to the
$T_{C}$
reduction.