Materials able to rapidly switch between thermally conductive states by external stimuli such as electric or magnetic fields can be used as all-solid-state thermal switches and open a myriad of applications in heat management, power generation and cooling. Here, we show that the large magnetoresistance that occurs in the highly conducting semimetal α-WSi2 single crystals leads to dramatically large changes in thermal conductivity at temperatures <100 K. At temperatures <20 K, where electron-phonon scattering is minimized, the thermal conductivity switching ratio between zero field and a 9T applied field can be >7. We extract the electronic and lattice components of the from the thermal conductivity measurements and show that the Lorenz number for this material approximates the theoretical value of L0. From the heat capacity and thermal diffusivity, the speed of thermal conductivity switching is estimated to range from 1 x 10−4 seconds at 5 K to 0.2 seconds at 100 K for a 5-mm long sample. This work shows that WSi2, a highly conducting multi-carrier semimetal, is a promising thermal switch component for low-temperature applications such cyclical adiabatic demagnetization cooling, a technique that would enable replacing 3He-based refrigerators.
@article{arxiv.2310.14467,
title = {Giant Magnetothermal Conductivity Switching in Semimetallic WSi$_{2}$ Single Crystals},
author = {Karl G. Koster and Jackson Hise and Joseph P. Heremans and Joshua E. Goldberger},
journal= {arXiv preprint arXiv:2310.14467},
year = {2024}
}