Dirac-like fermions anomalous magneto-transport in a spin-polarized oxide two-dimensional electron system

TL;DR

This study demonstrates a 2D electron system with ferromagnetic order, strong Rashba spin-orbit coupling, and Dirac-like fermions, exhibiting anomalous magneto-transport phenomena linked to Berry phase effects.

Contribution

It reports the design and realization of a spin-polarized 2DES with combined ferromagnetism and strong SOC at oxide interfaces, revealing novel quantum transport behaviors.

Findings

Observation of anomalous quantum corrections to magneto-conductance.

Emergence of a non-trivial Berry phase affecting electron back-scattering.

Phenomenology similar to gapped topological insulators.

Abstract

In two-dimensional electron systems (2DES) the breaking of the inversion, time-reversal and bulk crystal-field symmetries is interlaced with the effects of spin-orbit coupling (SOC) triggering exotic quantum phenomena. Here, we used epitaxial engineering to design and realize a 2DES characterized simultaneously by ferromagnetic order, large Rashba SOC and hexagonal band warping at the (111) interfaces between LaAlO$_{3}$, EuTiO$_{3}$ and SrTiO$_{3}$ insulators. The 2DES displays anomalous quantum corrections to the magneto-conductance driven by the time-reversal-symmetry breaking occurring below the magnetic transition temperature. The results are explained by the emergence of a non-trivial Berry phase and competing weak anti-localization / weak localization back-scattering of Dirac-like fermions, mimicking the phenomenology of gapped topological insulators. These findings open perspectives for the engineering of novel spin-polarized functional 2DES holding promises in spin-orbitronics and topological electronics.