$B^2$ to $B$-linear magnetoresistance due to impeded orbital motion

TL;DR

This paper proposes a fundamental principle explaining the ubiquitous linear magnetoresistance in strange metals, attributing it to regions on the Fermi surface that impede orbital motion, leading to a universal behavior across various correlated materials.

Contribution

It introduces a theoretical framework linking Fermi surface features to linear magnetoresistance, independent of specific material details.

Findings

Bounded sectors on the Fermi surface can cause B-linear magnetoresistance.

The theory accounts for the transition from quadratic to linear behavior.

Impeding orbital motion is a key mechanism in anomalous magnetotransport.

Abstract

Strange metals exhibit a variety of anomalous magnetotransport properties, the most striking of which is a resistivity that increases linearly with magnetic field $B$ over a broad temperature and field range. The ubiquity of this behavior across a spectrum of correlated metals - both single- and multi-band, with either dominant spin and/or charge fluctuations, of varying levels of disorder or inhomogeneity and in proximity to a quantum critical point or phase - obligates the search for a fundamental underlying principle that is independent of the specifics of any material. Strongly anisotropic (momentum-dependent) scattering can generate $B$-linear magnetoresistance but only at intermediate field strengths. At high enough fields, the magnetoresistance must eventually saturate. Here, we consider the ultimate limit of such anisotropy, a region or regions on the Fermi surface that impede all orbital (cyclotron) motion through them, but whose imposition can be modelled nonetheless through a modified Boltzmann theoretical treatment. Application of the proposed theorem suggests that the realization of quadratic-to-linear magnetoresistance requires the presence of a bounded sector on the Fermi surface possibly separating two distinct types of carriers. While this bounded sector may have different origins or manifestations, we expect its existence to account for the anomalous magnetotransport found in a wide range of correlated materials.