Quantum Kinetic Anatomy of Electron Angular Momenta Edge Accumulation

TL;DR

This paper uses quantum kinetic theory to analyze how electron spin and orbital angular momenta contribute to edge accumulation in metals, revealing new interband mechanisms affecting interpretations of experimental observations.

Contribution

It introduces a detailed partitioning of angular momentum responses into intraband and interband contributions, highlighting a new interband mechanism for orbital edge accumulation.

Findings

Spin and orbital Hall currents are purely intraband.

Intrinsic edge densities partly originate from a new interband mechanism.

Implications for interpreting orbital edge accumulation and current-induced torques.

Abstract

Controlling electron's spin and orbital degrees of freedom has been a major research focus over the past two decades, as it underpins the electrical manipulation of magnetization. Leveraging a recently introduced quantum kinetic theory of multiband systems [T. Valet and R. Raimondi, Phys. Rev. B 111, L041118 (2025)], we outline how the intrinsic angular momenta linear response is partitioned into intraband and interband contributions. Focusing on time reversal and inversion symmetric metals, we show that the spin and orbital Hall currents are purely intraband. We also reveal that the intrinsic edge densities originate partially, and in the orbital case probably mostly, from a new interband mechanism. We discuss how this profoundly impacts the interpretation of orbital edge accumulation observations, and has broader implications for current induced torques.