The inadequacy of the $\rho$-T curve for phase transitions in the presence of magnetic fields

TL;DR

This paper demonstrates that the $ ho(T)$ curve's indications of phase transitions in magnetic fields are often misleading, as magnetoresistance effects can mimic true phase changes, urging a reevaluation of transport data interpretation.

Contribution

The study reveals that magnetoresistance scaling, not actual phase transitions, explains reentrant metallic states, challenging traditional interpretations of $ ho(T)$ curves under magnetic influence.

Findings

Magnetoresistance effects can mimic phase transitions in $ ho(T)$ curves.

First-principles calculations explain reentrant behavior in SiP$_2$ and NbP.

Discrepancies in experimental magnetoresistance data are resolved.

Abstract

The $\rho(T)$ curve is traditionally employed to discern metallic, semiconductor, and insulating behaviors in materials, with any deviations often interpreted as indicative of phase transitions. However, does this interpretation hold under the influence of a magnetic field? Our research addresses this critical question by reevaluating the $\rho(T)$ curve in the presence of magnetic field. We uncover that metal-insulator shifts and reentrant metallic states may not indicate true phase transitions but rather originate from the scaling behavior of magnetoresistance, influenced by magnetic field and temperature through a power-law dependence. Employing advanced first-principles calculations and the Boltzmann method, we analyzed the magnetoresistance of SiP$_2$ and NbP across a range of conditions, successfully explaining not only the reentrant behavior observed in experiments but also resolving the discrepancies in magnetoresistance behavior reported by different research groups. These findings challenge the conventional use of the $\rho(T)$ curve as a straightforward indicator of phase transitions under magnetic conditions, highlighting the essential need to exclude typical magnetoresistance effects due to the Lorentz force before confirming such transitions. This novel insight reshapes our understanding of complex material properties in magnetic fields and sets a new precedent for the interpretation of transport phenomena in condensed matter physics.