The field dependence of electron effective mass in uranium superconductors

TL;DR

This paper investigates how the electron effective mass in uranium-based superconductors responds to magnetic fields, emphasizing the importance of direct measurements over resistivity-based inferences.

Contribution

It demonstrates that the field dependence of the resistivity coefficient A does not necessarily indicate a field-dependent effective mass, proposing de Haas-van Alphen measurements as a more direct method.

Findings

Resistivity coefficient A can vary with magnetic field even if the effective mass remains constant.

De Haas-van Alphen oscillations provide a direct way to assess effective mass dependence on magnetic field.

Field dependence of A does not always imply effective mass dependence, challenging previous assumptions.

Abstract

The magnetic field dependence of electron effective mass is an important subject in consideration of physical properties of superconducting ferromagnets URhGe, UCoGe and paramagnet UTe$_2$. It is usually accepted to find this dependence from the field dependence of $A$ coefficient in the low temperature resistivity law $\rho=\rho_0+AT^2$. It is shown here that the field dependence $A(H)$ takes place also for field-independent effective mass. Whether or not the effective mass depends on the magnetic field can be checked by the measurements of the amplitude of de Haas - van Alphen magnetisation oscillations.