Low temperature residual bulk resistivity in floating zone SmB₆ using the inverted resistance measurement

Samarium hexaboride (SmB₆) is a fascinating heavy-fermion system which appears to be the first correlated topological insulator with robust surface conduction and truly insulating bulk. We studied the low-temperature bulk transport of SmB₆ motivated by the magnetotorque report suggesting that the material might have an unconventional bulk Fermi surface. The bulk Fermi surface has been reported in SmB₆ crystals grown by the floating zone method. In electrical transport below ~4 K, there is a well-known resistance plateau that originates from the surface conduction. We found some of our SmB₆ crystals grown by the floating zone method show an absence of this resistance plateau, but instead a moderate resistance change. This resistance change is weak enough that it can be interpreted as the surface resistance plateau with a large temperature dependence. However, by using the inverted resistance technique, we clearly show that it originates from the bulk. The samples are being characterized using X-ray diffraction, Auger, high-resolution TEM, and energy dispersive X-Ray spectroscopy measurements with the goal of identifying differences between SmB₆ crystals grown by Al-flux and floating-zone methods.