Interfacial orbital transmission, conversion, and mechanical torque in metals

TL;DR

This paper provides a theoretical analysis of how orbital angular momentum is transmitted, converted, and can generate mechanical torque at metallic interfaces, highlighting the role of crystal fields and orbital dipoles.

Contribution

It introduces a model Hamiltonian to study interfacial orbital transport, revealing oscillations, quadrupole moments, and torque generation related to orbital dynamics.

Findings

Orbital dipoles oscillate due to crystal-field effects.

Orbital absorption leads to measurable mechanical torque.

Orbital memory loss occurs at interfaces.

Abstract

Interfacial orbital transport remains far less understood than its bulk counterpart despite its central role in orbitronic experiments. Here, we theoretically investigate the transmission and conversion of orbital angular momentum across a metallic interface using a model Hamiltonian incorporating crystal-field effects. We show that an injected orbital dipole moment undergoes pronounced oscillations driven by the crystal field and generates characteristic quadrupole moments determined by the orbital orientation relative to the interface. Unlike spin precession, the dipole relaxes toward a finite value away from the interface. We further quantify interfacial orbital memory loss and demonstrate that orbital absorption produces a sizable mechanical torque obtained from the orbital continuity equation.