  Controlling thermal transport is important for a range of devices and
technologies, from phase change memories to next-generation electronics. This
is especially true in nano-scale devices where thermal transport is altered by
the influence of surfaces and changes in dimensionality. In superconducting
nanowire single-photon detectors, the thermal boundary conductance (TBC)
between the nanowire and the substrate it is fabricated on influences most of
the performance metrics that make these detectors attractive for applications.
This includes the maximum count rate, latency, jitter, and quantum efficiency.
Despite its importance, the study of TBC in superconducting nanowire devices
has not been done systematically, primarily due to the lack of a
straightforward characterization method. Here, we show that simple electrical
measurements can be used to estimate the TBC between nanowires and substrates
and that these measurements match acoustic mismatch theory across a variety of
substrates. Numerical simulations allow us to refine our understanding,
however, open questions remain. This work should enable thermal engineering in
superconducting nanowire electronics and cryogenic detectors for improved
device performance.
