Comparing Cr-Doped (Bi_xSb_1-x)₂Te₃ to Graphene as a Future Platform for Quantum Hall Resistance Standards

Since 2017, epitaxial graphene has been the base material for the US national standard for resistance. Due to a relaxed magnetic field and temperature requirement, these graphene-based devices enabled more user-friendly access to the quantum Hall effect and could more easily be deployed into US and global industries compared to GaAs-based devices. A future avenue of research within electrical metrology is to remove the need for strong magnetic fields, as is currently the case for devices exhibiting the quantum Hall effect. New materials, like magnetically doped topological insulators (MTIs), offer access to the quantum anomalous Hall effect, which in its ideal form, could become a future resistance standard needing only a small permanent magnet to activate a quantized resistance value. Furthermore, these devices could operate at zero-field for measurements, making the dissemination of the ohm more economical and portable. Here we present results on precision measurements of the h/e^2 quantized plateau of Cr-Doped (Bi_xSb_1-x)₂Te₃ and give them context by comparing them to modern graphene-based resistance standards. Ultimately, MTI-based devices could be combined in a single system with magnetic-field-averse Josephson voltage standards to obtain an alternative quantum current standard.