Quasi-isotropic orbital magnetoresistance in lightly doped SrTiO$_{3}$

TL;DR

This paper reports a large, non-saturating, quasi-isotropic orbital magnetoresistance in lightly doped SrTiO₃, explained by magnetic field-induced mobility reduction and electron cyclotron motion in polar domain landscapes.

Contribution

It reveals a novel quasi-isotropic magnetoresistance in SrTiO₃ and links it to electron cyclotron motion and polar domain effects, challenging existing theories.

Findings

Magnetoresistance is independent of current and magnetic field orientation.

Mobility decreases smoothly with magnetic field across all directions.

Electron cyclotron motion in polar domains underpins the observed effect.

Abstract

A magnetic field parallel to an electrical current does not produce a Lorentz force on the charge carriers. Therefore, orbital longitudinal magnetoresistance is unexpected. Here we report on the observation of a large and non saturating magnetoresistance in lightly doped SrTiO$_{3-x}$ independent of the relative orientation of current and magnetic field. We show that this quasi-isotropic magnetoresistance can be explained if the carrier mobility along all orientations smoothly decreases with magnetic field. This anomalous regime is restricted to low concentrations when the dipolar correlation length is longer than the distance between carriers. We identify cyclotron motion of electrons in a potential landscape tailored by polar domains as the cradle of quasi-isotropic orbital magnetoresistance. The result emerges as a challenge to theory and may be a generic feature of lightly-doped quantum paralectric materials.