Characterization of Dislocation Conduction in Strained Bismuth Antimony Alloys using Corbino Geometry Contacts

BiSb is a semiconducting alloy that exhibits topological insulating properties at low temperatures when Sb concentration is between 7% and 22%. Lattice dislocations matching specific Burgers vectors are expected to host one dimensional, dissipationless conducting modes. To date, these modes have been challenging to study directly, as they cannot be accessed in isolation from the rest of the material. Dislocations are expected to manifest as an increase in bulk conductivity in the topological insulating state. However, quantifying bulk conductivity in the presence of far stronger surface conductivity, such as in a topological insulator, presents a great challenge. In the present study, we generate dislocations in topologically insulating BiSb single crystals, cleaved along the (111) plane, both by indenting them using a 100-um long wedge and by applying crystal-wide compressive strain. By using 4-Terminal Corbino rings placed on both dislocation-dense and pristine areas of these crystals, we aim to examine the bulk conductivity in isolation from surface conductivity, and derive a relationship between dislocation density and bulk conduction.