Magneto-orbital effect without spin-orbit interactions --- noncentrosymmetric zeolite-templated carbon structure

TL;DR

This paper predicts a novel magneto-orbital effect in a noncentrosymmetric carbon structure, where chiral orbital states lead to asymmetric band dispersion and potential current-induced orbital magnetism, independent of spin-orbit interactions.

Contribution

It introduces a new orbital magnetism mechanism in a noncentrosymmetric carbon system without relying on spin-orbit coupling, based on first-principles calculations.

Findings

Valence band top from chiral states with orbital moments of ±1

Asymmetric band dispersion due to lattice structure

Potential for current-induced orbital magnetism

Abstract

A peculiar manifestation of orbital angular momentum is proposed for a zeolite-templated carbon system, C36H9. The structure, being a network of nanoflakes in the shape of a "pinwheel", lacks inversion symmetry. While the unit cell is large, the electronic structure obtained with a first-principles density functional theory and captured as an effective tight-binding model in terms of maximally-localized Wannier functions, exhibits an unusual feature that the valence band top comes from two chiral states having orbital magnetic momenta of $\pm 1$. The noncentrosymmetric lattice structure then makes the band dispersion asymmetric, as reminiscent of, but totally different from, spin-orbit systems. The unusual feature is predicted to imply a current-induced orbital magnetism when holes are doped.