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Boundary conductance in macroscopic bismuth crystals
Woun Kang1, Felix Spathelf2,3, Benoît Fauqué3
1Department of Physics, Ewha Womans University, Seoul, 03760, Korea.
Nature Communications
|January 12, 2022
Summary
Researchers found a metallic surface conductivity in bismuth crystals when a magnetic field is applied parallel to the boundary. This robust effect, absent in antimony, highlights the link between band symmetry and boundary conductance in topological materials.
Area of Science:
- Condensed matter physics
- Materials science
- Surface science
Background:
- The interface between solids and vacuum can exhibit unique electronic properties, distinct from the bulk.
- Topologically protected metallic surface states in insulators are known to arise from non-trivial Berry curvature or driven perturbations.
Purpose of the Study:
- To investigate the electronic transport properties at the boundary of three-dimensional crystals.
- To explore the role of band symmetry in surface conductivity.
Main Methods:
- Angle-dependent magnetoresistance measurements on prismatic bismuth and antimony crystals.
- Comparative analysis of conductivity in bismuth and antimony under parallel magnetic fields.
Main Results:
- A robust surface contribution to electric conductivity was detected in bismuth when the magnetic field was parallel to the crystal-vacuum boundary.
- This boundary conductance effect was absent in antimony, despite similar crystal symmetry and carrier properties.
- The presence of the effect in bismuth aligns with theoretical predictions of metallic boundary states.
Conclusions:
- The study confirms the existence of a metallic boundary in bismuth, as predicted by Azbel.
- The absence of this effect in antimony underscores a critical link between band symmetry and boundary conductance in topological materials.
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