  Recent reports reveal that isothermal chemical doping of hydrogen in
correlated complex oxides such as perovskite nickelates (e.g. NdNiO3) can
induce a metal-to-insulator transition (MIT) without the need for temperature
modulation. In this work, we interrogate the magnitude change in temperature
dependence of thermal conductivity upon chemical doping of hydrogen, as any
changes to the thermal properties upon doping offer a route to solid-state
thermal switches as well as another potential signal to monitor in a diverse
set of sensing, electronic, and optical applications. Using frequency-domain
thermoreflectance, we demonstrate that a large concentration of hydrogen (~ 0.1
- 0.5 H/unit cell) completely suppresses the electronic contribution to thermal
conductivity in NdNiO3 thin films and reduces the phononic contribution by a
factor of 2. These results are critical for the design of next-generation
solid-state thermal switches, sensors, extreme environment electronics and
neuromorphic memory architectures.
