Bulk Electrical Transport studies of Magnetically doped SmB6

The past decade of samarium hexaboride (SmB₆) studies has challenged our fundamental understanding of the bulk gap of Kondo insulators. The non-trivial topology and the existence of possible chargeless fermions are current exciting directions in studying intrinsic properties of SmB₆. The extrinsic nature, including disorder, of SmB₆, is another exciting direction but a mystery at the same time. Using the inverted resistance technique to separate the bulk and surface conduction, the previous report of a 10-order-of-magnitude exponential increase of resistivity upon lowering the temperature suggests that the bulk gap is very robust against disorder. This questions whether an impurity band exists in the bulk gap of SmB6 and whether the transport response is identical to that of doped semiconductors like silicon. This also relates to one of the most fundamental questions: what is the true bulk gap dispersion and where is the chemical potential located? In this talk, we present bulk transport studies using the inverted resistance method and Hall effect on various Fe-, Gd- and Nd-doped SmB₆ single crystals to partially answer these questions.