  Plasmonic absorption of light can lead to significant local heating in
metallic nanostructures, an effect that defines the sub-field of
thermoplasmonics and has been leveraged in diverse applications from biomedical
technology to optoelectronics. Quantitatively characterizing the resulting
local temperature increase can be very challenging in isolated nanostructures.
By measuring the optically-induced change in resistance of metal nanowires with
a transverse plasmon mode, we quantitatively determine the temperature increase
in single nanostructures, with the dependence on incident polarization clearly
revealing the plasmonic heating mechanism. Computational modeling explains the
resonant and nonresonant contributions to the optical heating and the dominant
pathways for thermal transport. These results, obtained by combining electronic
and optical measurements, place a bound on the role of optical heating in prior
experiments, and suggest design guidelines for engineered structures meant to
leverage such effects.
