Circular Dichroism of Crystals from First Principles

Chiral crystals show promise for spintronic technologies on account of their efficient spin filtering. This has led to significant recent interest in quantitative characterization and first-principles prediction of their optoelectronic properties, elucidating connections between chiroptical and spin transport properties in chiral materials. Here, we outline a computational framework for efficient ab initio calculations of circular dichroism (CD) in crystalline materials. We leverage direct calculation of orbital angular momentum and quadrupole matrix element calculations in density-functional theory (DFT) and Wannier interpolation to calculate CD in complex materials, removing the need for band convergence and accelerating Brillouin-zone convergence compared to prior approaches. We find strong agreement with measured CD signals in molecules and crystals ranging in complexity from small bulk unit cells to 2D hybrid perovskites, and show the importance of the quadrupole contribution to the anisotropic CD in crystals. We leverage the tensorial behavior of CD with respect to propagation direction to analyze the strongly orientation-dependent CD of compex chiral crystals such as hybrid perovskites. Spin-orbit coupling affects the CD of crystals with heavier atoms, as expected, but this is primarily due to changes in the electronic energies, rather than due to direct contributions from the spin matrix elements.