Axis-dependent conduction polarity (ADCP) and nonsaturating magnetoresistance (MR) are distinct transport responses that both reflect anisotropic carrier dynamics governed by Fermi surface geometry. Here, we combine density functional theory and semiclassical Boltzmann transport calculations to investigate the evolution of magnetotransport in ${\mathrm{MgB}}_2$, a model system containing a band saddle point near the Fermi level. Tuning the chemical potential (μ) across the saddle point induces a Lifshitz transition with the emergence of open Fermi surface sheets. During this evolution, the calculated Hall response exhibits polarity reversal, whereas the magnetoresistance changes from saturating to nonsaturating behavior involving open orbits. Opposite Hall contributions from convex and concave portions of the same Fermi surface modify the degree of compensation and thereby shape the field dependence of the calculated magnetoresistance. Calculations for ${\mathrm{CaB}}_2$ and ${\mathrm{SrB}}_2$ reveal analogous Fermi surface features, extending the discussion to layered diborides. These results reveal a microscopic connection between ADCP and nonsaturating MR through the evolution of the Fermi surface and offer a basis for analyzing anisotropic magnetotransport in comparable materials.

Close

PrevNext

View figure in article

• Fermi surface
• Hall effect
• High magnetic fields
• Magnetoresistance
• Alkaline earth metals
• Boron family
• Hexagonal close-packed
• Boltzmann theory
• Density functional theory
• Tight-binding model
• Wannier function methods