Magnetically Tuned Superconducting Transition-Edge Sensors

In this work we present a detector model for superconducting transition-edge sensors (TESs) that includes for the first time the magnetic field dependence of the resistive transition. By writing the resistance
$R$
as a function of temperature
$T$
current
$I$
and magnetic field
$B$
we present a general result requiring few assumptions that offers a new strategy to improve TES performance. Application of our TES models that agree with measurements of the critical current on TES sensors predicts that it is possible to design and operate a TES in a new regime by magnetically tuning the resistive transition surface
$R(T, I, B)$
. We show using all realizable device parameter values that this new magnetically tuned transition surface is predicted to give a sensor with larger signal size, faster speed capability, reduced performance limiting Johnson noise, and improved energy resolution; and do so over the entire pulse trajectory in
$R(T, I, B)$
space. We emphasize that our result is robust in that the performance benefits listed do not hinge on a precise functional form of the resistive transition. This magnetic tuning technique can improve performance for TESs governed by a wide range of resistive mechanisms such as weakly coupled to strongly coupled superconductors or nonequilibrium superconductivity.