1
Conductivity Space Isotherm Behavior in Quantum Anomalous Hall
Devices
N. T. M. Tran
1,2†
, V. Ortiz Jimenez
1†
, M. Musso
3
, L. K. Rodenbach
4,5
, M. P.
Andersen
5,6
, H. M. Hill
1
, P. Zhang
7
, L. Tai
7
, K. L. Wang
7
, M. Marzano
8
, M.
Ortolano
3
, D. B. Newell
1
, C. A. Richter
1
, and A. F. Rigosi
1,a)
1
Physical Measurement Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland,
20899-8171, USA
2
Joint Quantum Institute, University of Maryland, College Park, MD 20742, USA
3
Department of Electronics and Telecommunications, Politecnico di Torino, Torino 10129, Italy
4
Department of Physics, Stanford University, Stanford, CA 94305, USA
5
Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025,
USA
6
Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305, USA
7
Department of Electrical Engineering, University of California, Los Angeles, CA 90095, USA
8
Istituto Nazionale di Ricerca Metrologica, Torino 10135, Italy
The quantum Hall effect (QHE) has enhanced accessibility to measure and disseminate electrical units, owed in part to the
recently redefined International System of Units (SI) in 2019. Graphene remains one of the preferred options to realize the
ohm despite the limitations of high magnetic fields to produce a robust QHE. Topological insulators, on the other hand, show
promise in providing quantized resistance via the quantum anomalous Hall effect (QAHE), a phenomenon that removes the
need for magnetic fields during operation. To optimize future devices for metrological applications, it is important to gain a
better understanding of magnetically doped topological insulators like Cr-doped bismuth antimony telluride. The application
of differential conductivity space analyses offers a more sensitive way to analyze the data and distinguish between 2D and 3D
transport behaviors. This is particularly important in thin films where the transition between 2D and 3D behavior can be
subtle. The ability to confidently determine the dimensionality of the transport is crucial for selecting appropriate theoretical
models for future device optimization. Furthermore, this work identifies variable range hopping as the dominant transport
mechanism in the 2D regime using a rigorous statistical analysis (via the Bayes factor). These elements assist in the
understanding of microscopic processes that govern charge transport in these materials.
_____________________________
a)
Author to whom correspondence should be addressed. Mail: Albert Rigosi, MS 8171, 100 Bureau Drive, NIST, Gaithersburg, MD 20899.
