Orbital magnetization of a metal is not a bulk property in the mesoscopic regime

TL;DR

This paper demonstrates that in the mesoscopic regime, surface modifications can significantly alter the magnetic moment of a metal, challenging the notion that orbital magnetization is solely a bulk property.

Contribution

It reveals that surface perturbations can cause extensive changes in magnetic moments in the mesoscopic regime, unlike in the macroscopic case where effects cancel out.

Findings

Surface modifications induce large changes in magnetic moment in mesoscopic systems.

Bulk effects cancel in macroscopic regime, but not in mesoscopic regime.

Surface perturbations can alter electron wavefunctions and angular momentum contributions.

Abstract

We find that, in the mesoscopic regime, modification of the material's surface can induce an extensive change of the material's magnetic moment. In other words, perturbation of order $N^2$ atoms on the surface of a 3-dimensional solid can change the magnetic moment proportionally to $N^3$. When the solid's surface is perturbed, it triggers two changes in the magnetization. One arises from variations of the electron wavefunction and energy, while the other arises from a modification in the kinetic angular momentum operator. In the macroscopic regime of our model, these two bulk effects cancel each other, resulting in no impact of the surface perturbation on the magnetization - consistent with prior work. In the mesoscopic regime, we find a departure from this behavior, as the cancelation of two terms is not complete.