Probing TES Transitions by Lead-Position- Dependent Resistance Measurement

We explore the possibility of studying the transition physics of transition edge sensor (TES) devices by performing resistance measurement on voltage leads that are fabricated at different locations along the sample edge. Our Scheme is based on the premise that how the measured resistance depends on the positions of the voltage and current leads are dictated by the underlying physics of the device. To verify its validity and effectiveness, we measure the position dependence of the resistance at temperatures above the critical temperature of the TES, where it is known to obey Ohm's law, and find that the results are in excellent agreement with theoretical predictions. We then perform preliminary measurement in the transition region, by using a superconducting quantum interference device (SQUID) sensor and a lock-in amplifier in a voltage biased circuit subject to a small ac stimulus. Although no theoretical models are available for comparison, the results show significant discrepancy from normal state values and indicate nonuniformity in the TES sample in the transition region. Our technique can be used in further studies to probe TES devices with more conventional lead designs and help understand their transition physics, which can lead to improved device design and operation.