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-WSi 2 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 L 0 . 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 WSi 2, 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 3 He-based refrigerators.