The quantum metric of electrons with spin-momentum locking

TL;DR

This paper demonstrates that spin-momentum locking in spin-orbit coupled materials induces a finite quantum metric, leading to a measurable nonlinear magnetoresistance at interfaces, revealing new quantum geometric effects.

Contribution

It reveals that spin-momentum locking causes quantum metric effects in a broad class of materials, enabling new functionalities based on quantum geometry.

Findings

Quantum metric induces nonlinear in-plane magnetoresistance.

Magnetoresistance can be electrically controlled.

Quantum metric effects are present in various materials.

Abstract

Quantum materials are characterized by electromagnetic responses intrinsically linked to the geometry and topology of electronic wavefunctions, encoded in the quantum metric and Berry curvature. Whereas Berry curvature-mediated transport effects have been identified in several magnetic and nonmagnetic systems, quantum metric-induced transport phenomena remain limited to topological antiferromagnets. Here we show that spin-momentum locking -- a general characteristic of the electronic states at surfaces and interfaces of spin-orbit coupled materials -- leads to a finite quantum metric. This metric activates a nonlinear in-plane magnetoresistance that we measure and electrically control in 111-oriented LaAlO$_3$/SrTiO$_3$ interfaces. These findings demonstrate the existence of quantum metric effects in a vast class of materials and enable previously unexplored strategies to design functionalities based on quantum geometry.