Year: 2020
Type: article
Abstract: The magnetic circular dichroism sum rule yields an extremely useful ground-state observable, which provides a quantitative measure of spontaneous time-reversal symmetry breaking (T-breaking) in a given material.Here I derive its explicit expression within band structure theory, in the general case: trivial insulators, topological insulators, and metals.Orbital magnetization provides a different measure of T-breaking in the electronic ground state.The two observables belong to the class of "geometrical" observables; both are local and admit a "density" in coordinate space.In both of them, one could include or exclude selected groups of bands in order to acquire element-specific information about the T-breaking material.Only in the case of an isolated flat band do the contributions to the two observables coincide.Finally, I provide the corresponding geometrical formula-in a different Hilbert space-for a many-body interacting system.
Source: Physical Review Research
Author: Raffaele Resta
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,625
Funder: Office of Naval Research
Awards: G399308035, G4504108201, G8876996369
OpenAlex ID: W3010350694