Giant Magnetothermal Conductivity Switching in Semimetallic WSi₂ Single Crystals

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 enable a myriad of applications in heat management, power generation, and cooling. Here, we show that the large magnetoresistance which occurs in 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 9 T applied field can be >7. We extract the electronic and lattice components of the thermal conductivity 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 × 10–4 s at 5 K to 0.2 s at 100 K for a 5 mm long sample. This work shows that WSi2, a highly conducting multicarrier semimetal, is a promising thermal switch component for low-temperature applications such as cyclical adiabatic demagnetization cooling, a technology that could replace 3He-based refrigerators.